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This chapter describes the commands used to perform basic system management tasks, such as naming the router and setting time services.
For basic system management configuration tasks and examples, refer to the chapter entitled "Performing Basic System Management" in the Configuration Fundamentals Configuration Guide.
To create a command alias, use the alias global configuration command. Use the no form of this command to delete all aliases in a command mode or to delete a specific alias, and to revert to the original command syntax.
alias mode alias-name alias-command-line
Syntax Description
mode Command mode of the original and alias commands. See Table 94 for a list of options for this argument. alias-name Command alias. alias-command-line Original command syntax.
Defaults
Default aliases are in EXEC mode as follows:
Command Alias | Original Command |
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Command Modes
Global configuration
Command History
10.3 This command was introduced.
Release
Modification
Usage Guidelines
You can use simple words or abbreviations as aliases. The aliases in the "Defaults" section are predefined. They can be turned off using the no alias command.
Table 94 shows the acceptable options for the mode argument in the alias global configuration command.
| Argument Options | Mode |
|---|---|
configuration | Global configuration |
controller | Controller configuration |
exec | EXEC |
hub | Hub configuration |
interface | Interface configuration |
ipx-router | IPX router configuration |
line | Line configuration |
map-class | Map class configuration |
map-list | Map list configuration |
route-map | Route map configuration |
router | Router configuration |
See the summary of command modes in the "Using the Command Line Interface" chapter in the Configuration Fundamentals Configuration Guide for more information about command modes.
When you use online help, command aliases are indicated by an asterisk (*), as follows:
Router#lo? *lo=logout lock login logout
When you use online help, aliases that contain spaces (for example, telnet device.cisco.com 25) are displayed as follows:
Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# alias exec device-mail telnet device.cisco.com 25 Router(config)# end Router# device-mail? *device-mail="telnet device.cisco.com 25"
When you use online help, the alias is expanded and replaced with the original command, as shown in the following example with the td alias:
Router(config)# alias exec td trace device Router(config)# ^Z Router# t? *td="trace device" telnet terminal test tn3270 trace
To list only commands and omit aliases, begin your input line with a space. In the following example, the alias td is not shown, because there is a space before the t? command line.
Router# t? telnet terminal test tn3270 trace
As with commands, you can use online help to display the arguments and keywords that can follow a command alias. In the following example, the alias td is created to represent the command telnet device. The /debug and /line switches can be added to telnet device to modify the command:
Router(config)# alias exec td telnet device
Router(config)# ^Z
Router# td ?
/debug Enable telnet debugging mode
/line Enable telnet line mode
...
whois Whois port
<cr>
Router# telnet device
You must enter the complete syntax for the alias command. Partial syntax for aliases are not accepted. In the following example, the parser does not recognize the command t as indicating the alias td.
Router# t % Ambiguous command: "t"
Examples
The following example creates the alias fixmyrt for the IP route198.92.116.16:
alias exec fixmyrt clear ip route 198.92.116.16
Related Commands
Displays all alias commands.
Command
Description
Use the buffers global configuration command to make adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed. Use the no form of this command to return the buffers to their default size.
buffers {small | middle | big | verybig | large | huge | type number} {permanent | max-free
Syntax Description
small Buffer size of this public buffer pool is 104 bytes. middle Buffer size of this public buffer pool is 600 bytes. big Buffer size of this public buffer pool is 1524 bytes. verybig Buffer size of this public buffer pool is 4520 bytes. large Buffer size of this public buffer pool is 5024 bytes. huge Default buffer size of this public buffer pool is 18024 bytes. This value can be configured with the buffers huge size command. type number Interface type and interface number of the interface buffer pool. The type value cannot be fddi. permanent Number of permanent buffers that the system tries to create and keep. Permanent buffers are normally not trimmed by the system. max-free Maximum number of free or unallocated buffers in a buffer pool. min-free Minimum number of free or unallocated buffers in a buffer pool. initial Number of additional temporary buffers that are to be allocated when the system is reloaded. This keyword can be used to ensure that the system has necessary buffers immediately after reloading in a high-traffic environment. number Number of buffers to be allocated.
A maximum of 20,480 small buffers can be constructed in the pool.
Defaults
The default number of buffers in a pool is determined by the hardware configuration and can be displayed with the EXEC show buffers command.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Normally you need not adjust these parameters; do so only after consulting with technical support personnel. Improper settings can adversely impact system performance.
You cannot configure FDDI buffers.
Examples of Public Buffer Pool Tuning
The following example keeps at least 50 small buffers free in the system:
buffers small min-free 50
The following example increases the permanent buffer pool allocation for big buffers to 200:
buffers big permanent 200
Example of Interface Buffer Pool Tuning
A general guideline is to display buffers with the show buffers command, observe which buffer pool is depleted, and increase that one.
The following example increases the permanent Ethernet 0 interface buffer pool on a Cisco 4000 is 96 because the Ethernet 0 buffer pool is depleted:
buffers ethernet 0 permanent 96
Related Commands
Changes the length of time for which data is used to compute load statistics. Displays statistics for the buffer pools on the network server.
Command
Description
Use the buffers huge size global configuration command to dynamically resize all huge buffers to the value you specify. Use the no form of this command to restore the default buffer values.
buffers huge size number
Syntax Description
number Huge buffer size, in bytes.
Defaults
18024 bytes
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use only after consulting with technical support personnel. The buffer size cannot be lowered below the default.
Examples
The following example resizes huge buffers to 20000 bytes:
buffers huge size 20000
Related Commands
Makes adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed. Displays statistics for the buffer pools on the network server.
Command
Description
To set the system calendar, use one of the formats of the calendar set EXEC command.
calendar set hh:mm:ss day month year
Syntax Description
hh:mm:ss Current time in hours (military format), minutes, and seconds. day Current day (by date) in the month. month Current month (by name). year Current year (no abbreviation).
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. After you set the calendar, the system clock will be automatically set from the calendar when the system is restarted or when the clock read-calendar EXEC command is issued. The time specified in this command is relative to the configured time zone.
Examples
The following example manually sets the system calendar to 1:32 p.m. on July 23, 1997:
calendar set 13:32:00 23 July 1997
Related Commands
Manually reads the calendar into the system clock. Manually set the system clock. Configures the system to automatically switch to summer time (daylight savings time). Sets the time zone for display purposes. Sets the calendar from the system clock.
Command
Description
To configure a router as a time source for a network based on its calendar, use the clock calendar-valid global configuration command. Use the no form of this command to specify that the calendar is not an authoritative time source.
clock calendar-validSyntax Description
This command has no arguments or keywords.
Defaults
The router is not configured as a time source.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. If you have no outside time source available on your network, use this command to make the calendar an authoritative time source.
Examples
The following example configures a router as the time source for a network based on its calendar:
clock calendar-valid
Related Commands
Configures the Cisco IOS software as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available. vines time use-system Sets VINES network time based on the internal time.
Command
Description
To manually read the calendar into the system clock, use the clock read-calendar EXEC command.
clock read-calendarSyntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted. When the router is rebooted, the calendar is automatically read into the system clock. However, you may use this command to manually read the calendar setting into the system clock. This command is useful if the calendar set command has been used to change the setting of the calendar.
Examples
The following example configures the system clock to set its date and time by the calendar setting:
clock read-calendar
Related Commands
Sets the system calendar. Manually set the system clock. Sets the calendar from the system clock. Periodically updates the calendar from Network Time Protocol (NTP).
Command
Description
To manually set the system clock, use one of the formats of the clock set EXEC command.
clock set hh:mm:ss day month year
Syntax Description
hh:mm:ss Current time in hours (military format), minutes, and seconds. day Current day (by date) in the month. month Current month (by name). year Current year (no abbreviation).
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Generally, if the system is synchronized by a valid outside timing mechanism, such as an NTP or VINES clock source, or if you have a router with calendar capability, you do not need to set the system clock. Use this command if no other time sources are available. The time specified in this command is relative to the configured time zone.
Examples
The following example manually sets the system clock to 1:32 p.m. on July 23, 1997:
clock set 13:32:00 23 July 1997
Related Commands
Sets the system calendar. Manually reads the calendar into the system clock. Configures the system to automatically switch to summer time (daylight savings time). Sets the time zone for display purposes.
Command
Description
To configure the system to automatically switch to summer time (daylight savings time), use one of the formats of the clock summer-time global configuration command. Use the no form of this command to configure the Cisco IOS software not to automatically switch to summer time.
clock summer-time zone recurring [week day month hh:mm week day month hh:mm [offset]]
Syntax Description
zone Name of the time zone (PDT,...) to be displayed when summer time is in effect. recurring Indicates that summer time should start and end on the corresponding specified days every year. date Indicates that summer time should start on the first specific date listed in the command and end on the second specific date in the command. week Week of the month (1 to 5 or last). day Day of the week (Sunday, Monday,...). date Date of the month (1 to 31). month Month (January, February,...). year Year (1993 to 2035). hh:mm Time (military format) in hours and minutes. offset (Optional) Number of minutes to add during summer time (default is 60).
Defaults
Summer time is disabled. If clock summer-time zone recurring is specified without parameters, the summer time rules default to United States rules. Default of offset is 60.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command if you want to automatically switch to summer time (for display purposes only). Use the recurring form of the command if the local summer time rules are of this form. Use the date form to specify a start and end date for summer time if you cannot use the first form.
In both forms of the command, the first part of the command specifies when summer time begins, and the second part specifies when it ends. All times are relative to the local time zone. The start time is relative to standard time. The end time is relative to summer time. If the starting month is after the ending month, the system assumes that you are in the Southern Hemisphere.
Examples
The following example specifies that summer time starts on the first Sunday in April at 02:00 and ends on the last Sunday in October at 02:00:
clock summer-time PDT recurring 1 Sunday April 2:00 last Sunday October 2:00
If you live in a place where summer time does not follow the pattern in the first example, you could set it to start on October 12, 1997 at 02:00, and end on April 26, 1998 at 02:00, with the following example:
clock summer-time date 12 October 1997 2:00 26 April 1998 2:00
Related Commands
Sets the system calendar. Sets the time zone for display purposes.
Command
Description
To set the time zone for display purposes, use the clock timezone global configuration command. To set the time to Coordinated Universal Time (UTC), use the no form of this command.
clock timezone zone hours [minutes]
Syntax Description
zone Name of the time zone to be displayed when standard time is in effect. hours Hours offset from UTC. minutes (Optional) Minutes offset from UTC.
Defaults
UTC
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The system internally keeps time in UTC, so this command is used only for display purposes and when the time is manually set.
Examples
The following example sets the timezone to Pacific Standard Time and offsets 8 hours behind UTC:
clock timezone PST -8
Related Commands
Sets the system calendar. Manually set the system clock. Configures the system to automatically switch to summer time (daylight savings time). Displays the system clock.
Command
Description
To set the calendar from the system clock, use the clock update-calendar EXEC command.
clock update-calendarSyntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.
If the system clock and calendar are not synchronized, and the system clock is more accurate, use this command to update the calendar to the correct date and time.
Examples
The following example copies the current time from the system clock to the calendar:
clock update-calendar
Related Commands
Manually reads the calendar into the system clock. Periodically updates the calendar from Network Time Protocol (NTP).
Command
Description
To generate a configuration that is compatible with an earlier Cisco IOS release, use the downward-compatible-config global configuration command. To remove this feature, use the no form of this command.
downward-compatible-config version
Syntax Description
version Cisco IOS Release number, not earlier than 10.2.
Defaults
Disabled
Command Modes
Global configuration
Command History
11.1 This command was introduced.
Release
Modification
Usage Guidelines
In Cisco IOS Release 10.3, IP access lists changed format. Use this command to regenerate a configuration in a format prior to Release 10.3 if you are going to downgrade from a Release 10.3 or later to an earlier release. The earliest release this command accepts is 10.2.
When this command is configured, the router attempts to generate a configuration that is compatible with the specified version. Currently, this command affects only IP access lists.
Under some circumstances, the software might not be able to generate a fully backward-compatible configuration. In such a case, the software issues a warning message.
Examples
The following example generates a configuration file compatible with Cisco IOS Release 10.2:
downward-compatible-config 10.2
Related Commands
access-list (extended) Provides extended access lists that allow more detailed access lists. access-list (standard) Defines a standard XNS access list.
Command
Description
To specify or modify the host name for the network server, use the hostname global configuration command. The host name is used in prompts and default configuration filenames. The setup command facility also prompts for a host name at startup.
hostname name
Syntax Description
name New host name for the network server.
Defaults
The factory-assigned default host name is router.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The order of display at startup is banner message-of-the-day (MOTD), then login and password prompts, then EXEC banner.
Do not expect case to be preserved. Upper- and lowercase characters look the same to many internet software applications (often under the assumption that the application is doing you a favor). It may seem appropriate to capitalize a name the same way you might do in English, but conventions dictate that computer names appear all lowercase. For more information, refer to RFC 1178, Choosing a Name for Your Computer.
The name must also follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphens. Names must be 63 characters or fewer. For more information, refer to RFC 1035, Domain Names--Implementation and Specification.
Examples
The following example changes the host name to sandbox:
hostname sandbox
Related Commands
setup Enables you to make major enhancements to your configurations, for example, adding a protocol suit, making major addressing scheme changes, or configuring newly installed interfaces.
Command
Description
Syntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
By default, the BOOTP server is enabled.
When you disable the BOOTP server, access to the BOOTP ports cause the Cisco IOS software to send an "ICMP port unreachable" message to the sender and discard the original incoming packet.
 |
Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings, whether or not you have changed the default using the no ip bootp server command. |
Examples
The following example disables the BOOTP service on the router:
no ip bootp server
Use the ip telnet source-interface global configuration command to allow a user to select an address of an interface as the source address for Telnet connections. Use the no form of this command to reset the source address to the default for each connection.
ip telnet source-interface interface
Syntax Description
interface The interface whose address is to be used as the source for Telnet connections.
Defaults
The address of the closest interface to the destination as the source address. If the selected interface is not "up," the Cisco IOS software selects the address of the closest interface to the destination as the source address.
Command Modes
Global configuration
Command History
11.1 This command was introduced.
Release
Modification
Usage Guidelines
Use this command to set an interface's IP address as the source for all Telnet connections.
Examples
The following example makes the IP address for Ethernet interface 1 as the source address for Telnet connections:
ip telnet source-interface e 1
Related Commands
ip radius source-interface Forces RADIUS to use the IP address of a specified interface for all outgoing RADIUS packets.
Command
Description
Use the ip tftp source-interface global configuration command to allow a user to select the interface whose address will be used as the source address for TFTP connections.
ip tftp source-interface interface
Syntax Description
interface The interface whose address is to be used as the source for TFTP connections.
Defaults
The address of the closest interface to the destination as the source address. If the selected interface is not "up," the Cisco IOS software selects the address of the closest interface to the destination as the source address.
Command Modes
Global configuration
Command History
11.1 This command was introduced.
Release
Modification
Usage Guidelines
Use this command to set an interface's IP address as the source for all TFTP connections.
Examples
The following example makes the IP address for Ethernet interface 1 as the source address for TFTP connections:
ip tftp source-interface e 1
Related Commands
ip radius source-interface Forces RADIUS to use the IP address of a specified interface for all outgoing RADIUS packets.
Command
Description
Syntax Description
seconds Length of time for which data is used to compute load statistics. A value that is a multiple of 30, from 30 to 600 (30, 60, 90, 120, and so forth).
Defaults
300 seconds (or 5 minutes)
Command Modes
Interface configuration
Command History
10.3 This command was introduced.
Release
Modification
Usage Guidelines
If you want load computations to be more reactive to short bursts of traffic, rather than averaged over 5-minute periods, you can shorten the length of time over which load averages are computed.
If the load interval is set to 30 seconds, new data is used for load calculations over a 30-second period. This data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability.
Load data is gathered every 5 seconds. This data is used for a weighted average calculation in which more-recent load data has more weight in the computation than older load data. If the load interval is set to 30 seconds, the average is computed for the last 30 seconds of load data.
The load-interval command allows you to change the default interval of 5 minutes to a shorter or longer period of time. If you change it to a shorter period of time, the input and output statistics that are displayed when you use the show interface command will be more current, and based on more instantaneous data, rather than reflecting a more average load over a longer period of time.
This command is often used for dial backup purposes, to increase or decrease the likelihood of a backup interface being implemented, but it can be used on any interface.
Examples
In the following example, the default 5-minute average is set it to a 30-second average. A burst in traffic that would not trigger a dial backup for an interface configured with the default 5-minute interval might trigger a dial backup for this interface that is set for a shorter, 30-second interval.
interface serial 0 load-interval 30
Related Commands
show interfaces Use the show interfaces EXEC command to display ALC information.
Command
Description
To control access to the system's Network Time Protocol (NTP) services, use the ntp access-group global configuration command. To remove access control to the system's NTP services, use the no form of this command.
ntp access-group {query-only | serve-only | serve | peer} access-list-number
Syntax Description
query-only Allows only NTP control queries. See RFC 1305 (NTP version 3). serve-only Allows only time requests. serve Allows time requests and NTP control queries, but does not allow the system to synchronize to the remote system. peer Allows time requests and NTP control queries and allows the system to synchronize to the remote system. access-list-number Number (1 to 99) of a standard IP access list.
Defaults
No access control (full access granted to all systems)
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The access group options are scanned in the following order from least restrictive to most restrictive:
1. peer
2. serve
3. serve-only
4. query-only
Access is granted for the first match that is found. If no access groups are specified, all access is granted to all sources. If any access groups are specified, only the specified access is granted. This facility provides minimal security for the time services of the system. However, it can be circumvented by a determined programmer. If tighter security is desired, use the NTP authentication facility.
Examples
The following example configures the system to allow itself to be synchronized by a peer from access list 99. However, the system restricts access to allow only time requests from access list 42.
ntp access-group peer 99 ntp access-group serve-only 42
Related Commands
access-list Configures the access list mechanism for filtering frames by protocol type or vendor code.
Command
Description
To enable Network Time Protocol (NTP) authentication, use the ntp authenticate global configuration command. Use the no form of this command to disable the feature.
ntp authenticateSyntax Description
This command has no arguments or keywords.
Defaults
No authentication
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command if you want authentication. If this command is specified, the system will not synchronize to a system unless it carries one of the authentication keys specified in the ntp trusted-key command.
Examples
The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:
ntp authenticate ntp authentication-key 42 md5 aNiceKey ntp trusted-key 42
Related Commands
Defines an authentication key for Network Time Protocol (NTP). Authenticates the identity of a system to which Network Time Protocol (NTP) will synchronize.
Command
Description
To define an authentication key for Network Time Protocol (NTP), use the ntp authentication-key global configuration command. Use the no form of this command to remove the authentication key for NTP.
ntp authentication-key number md5 value
Syntax Description
number Key number (1 to 4294967295). md5 Authentication key. Message authentication support is provided using the Message Digest (MD5) algorithm. The key type md5 is currently the only key type supported. value Key value (an arbitrary string of up to eight characters).
Defaults
No authentication key is defined for NTP.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command to define authentication keys for use with other NTP commands in order to provide a higher degree of security.
|
Note When this command is written to NVRAM, the key is encrypted so that it is not displayed when the configuration is viewed. |
Examples
The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:
ntp authenticate ntp authentication-key 42 md5 aNiceKey ntp trusted-key 42
Related Commands
Enables Network Time Protocol (NTP) authentication. Configures the system clock to synchronize a peer or to be synchronized by a peer. Allows the system clock to be synchronized by a time server. Authenticates the identity of a system to which Network Time Protocol (NTP) will synchronize.
Command
Description
To specify that a specific interface should send Network Time Protocol (NTP) broadcast packets, use the ntp broadcast interface configuration command. Use the no form of this command to disable this capability.
ntp broadcast [version number]
Syntax Description
version number (Optional) Number from 1 to 3 indicating the NTP version.
Defaults
Disabled
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
Examples
The following example configures Ethernet interface 0 to send NTP version 2 packets:
interface ethernet 0 ntp broadcast version 2
Related Commands
Allows the system to receive NTP broadcast packets on an interface. Sets the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server.
Command
Description
To allow the system to receive NTP broadcast packets on an interface, use the ntp broadcast client interface configuration command. Use the no form of this command to disable this capability.
ntp broadcast clientSyntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command to allow the system to listen to broadcast packets on an interface-by-interface basis.
Examples
The following example synchronizes the Cisco IOS software to NTP packets broadcast on Ethernet interface 1:
interface ethernet 1 ntp broadcast client
Related Commands
Specifies that a specific interface should send Network Time Protocol (NTP) broadcast packets. Sets the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server.
Command
Description
To set the estimated round-trip delay between the Cisco IOS software and a Network Time Protocol (NTP) broadcast server, use the ntp broadcastdelay global configuration command. Use the no form of this command to revert to the default value.
ntp broadcastdelay microseconds
Syntax Description
microseconds Estimated round-trip time (in microseconds) for NTP broadcasts. The range is from 1 to 999999.
Defaults
3000 microseconds
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command when the router is configured as a broadcast client and the round-trip delay on the network is other than 3000 microseconds.
Examples
The following example sets the estimated round-trip delay between a router and the broadcast client to 5000 microseconds:
ntp broadcastdelay 5000
Related Commands
Specifies that a specific interface should send Network Time Protocol (NTP) broadcast packets. Allows the system to receive NTP broadcast packets on an interface.
Command
Description
As NTP compensates for the error in the system clock, it keeps track of the correction factor for this error. The system automatically saves this value into the system configuration using the ntp clock-period global configuration command. The system uses the no form of this command to revert to the default.
ntp clock-period value |
Caution Do not enter this command; it is documented for informational purposes only. The system automatically generates this command as Network Time Protocol (NTP) determines the clock error and compensates. |
Syntax Description
value Amount to add to the system clock for each clock hardware tick (in units of
2-32 seconds).
Defaults
17179869 2-32 seconds (4 milliseconds)
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
If a copy running-config startup-config command is entered to save the configuration to NVRAM, this command will automatically be added to the configuration. It is a good idea to perform this task after NTP has been running for a week or so; this will help NTP synchronize more quickly if the system is restarted.
To prevent an interface from receiving Network Time Protocol (NTP) packets, use the ntp disable interface configuration command. To enable receipt of NTP packets on an interface, use the no form of this command.
ntp disableSyntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
This command provides a simple method of access control.
Examples
The following example prevents Ethernet interface 0 from receiving NTP packets:
interface ethernet 0 ntp disable
To configure the Cisco IOS software as a Network Time Protocol (NTP) master clock to which peers synchronize themselves when an external NTP source is not available, use the ntp master global configuration command. To disable the master clock function, use the no form of this command.
ntp master [stratum] |
Caution Use this command with extreme caution. It is very easy to override valid time sources using this command, especially if a low stratum number is configured. Configuring multiple machines in the same network with the ntp master command can cause instability in keeping time if the machines do not agree on the time. |
Syntax Description
stratum (Optional) Number from 1 to 15. Indicates the NTP stratum number that the system will claim.
Defaults
By default, the master clock function is disabled. When enabled, the default stratum is 8.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Because Cisco's implementation of NTP does not support directly attached radio or atomic clocks, the router is normally synchronized, directly or indirectly, to an external system that has such a clock. In a network without Internet connectivity, such a time source may not be available. The ntp master command is used in such cases.
If the system has ntp master configured, and it cannot reach any clock with a lower stratum number, the system will claim to be synchronized at the configured stratum number, and other systems will be willing to synchronize to it via NTP.
|
Note The system clock must have been set from some source, including manually, before ntp master will have any effect. This protects against distributing erroneous time after the system is restarted. |
Examples
The following example configures a router as an NTP master clock to which peers may synchronize:
ntp master 10
Related Commands
Configures a router as a time source for a network based on its calendar.
Command
Description
To configure the system clock to synchronize a peer or to be synchronized by a peer, use the
ntp peer global configuration command. To disable this capability, use the no form of this command.
Syntax Description
ip-address IP address of the peer providing, or being provided, the clock synchronization. version (Optional) Defines the Network Time Protocol (NTP) version number. number (Optional) NTP version number (1 to 3). key (Optional) Defines the authentication key. keyid (Optional) Authentication key to use when sending packets to this peer. source (Optional) Names the interface. interface (Optional) Name of the interface from which to pick the IP source address. prefer (Optional) Makes this peer the preferred peer that provides synchronization.
Defaults
No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command if you want to allow this machine to synchronize with the peer, or vice versa. Using the prefer keyword reduces switching back and forth between peers.
If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.
Examples
The following example configures a router to allow its system clock to be synchronized with the clock of the peer (or vice versa) at IP address 192.168.22.33 using NTP version 2. The source IP address is the address of Ethernet 0.
ntp peer 192.168.22.33 version 2 source ethernet 0
Related Commands
Defines an authentication key for Network Time Protocol (NTP). Allows the system clock to be synchronized by a time server. Uses a particular source address in Network Time Protocol (NTP) packets.
Command
Description
To allow the system clock to be synchronized by a time server, use the ntp server global configuration command. To disable this capability, use the no form of this command.
ntp server ip-address [version number] [key keyid] [source interface] [prefer]
Syntax Description
ip-address IP address of the time server providing the clock synchronization. version (Optional) Defines the Network Time Protocol (NTP) version number. number (Optional) NTP version number (1 to 3). key (Optional) Defines the authentication key. keyid (Optional) Authentication key to use when sending packets to this peer. source (Optional) Identifies the interface from which to pick the IP source address. interface (Optional) Name of the interface from which to pick the IP source address. prefer (Optional) Makes this server the preferred server that provides synchronization.
Defaults
No peers are configured by default. If a peer is configured, the default NTP version number is 3, no authentication key is used, and the source IP address is taken from the outgoing interface.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
This command first appeared in Cisco IOS Release.
Use this command if you want to allow this machine to synchronize with the specified server. The server will not synchronize to this machine.
Using the prefer keyword reduces switching back and forth between servers.
If you are using the default version of 3 and NTP synchronization does not occur, try using NTP version number 2. Many NTP servers on the Internet run version 2.
Examples
The following example configures a router to allow its system clock to be synchronized with the clock of the peer at IP address 172.16.22.44 using NTP version 2:
ntp server 172.16.22.44 version 2
Related Commands
Defines an authentication key for Network Time Protocol (NTP). Configures the system clock to synchronize a peer or to be synchronized by a peer. Uses a particular source address in Network Time Protocol (NTP) packets.
Command
Description
To use a particular source address in Network Time Protocol (NTP) packets, use the ntp source global configuration command. Use the no form of this command to remove the specified source address.
ntp source type number
Syntax Description
type Type of interface. number Number of the interface.
Defaults
Source address is determined by the outgoing interface.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Use this command when you want to use a particular source IP address for all NTP packets. The address is taken from the named interface. This command is useful if the address on an interface cannot be used as the destination for reply packets. If the source keyword is present on an ntp server or ntp peer command, that value overrides the global value.
Examples
The following example configures a router to use the IP address of Ethernet 0 as the source address of all outgoing NTP packets:
ntp source ethernet 0
Related Commands
Configures the system clock to synchronize a peer or to be synchronized by a peer. Allows the system clock to be synchronized by a time server.
Command
Description
To authenticate the identity of a system to which Network Time Protocol (NTP) will synchronize, use the ntp trusted-key global configuration command. Use the no form of this command to disable authentication of the identity of the system.
ntp trusted-key key-number
Syntax Description
key-number Key number of authentication key to be trusted.
Defaults
Disabled
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
If authentication is enabled, use this command to define one or more key numbers (corresponding to the keys defined with the ntp authentication-key command) that a peer NTP system must provide in its NTP packets, in order for this system to synchronize to it. This provides protection against accidentally synchronizing the system to a system that is not trusted, since the other system must know the correct authentication key.
Examples
The following example configures the system to synchronize only to systems providing authentication key 42 in its NTP packets:
ntp authenticate ntp authentication-key 42 md5 aNiceKey ntp trusted-key 42
Related Commands
Enables Network Time Protocol (NTP) authentication. Defines an authentication key for Network Time Protocol (NTP).
Command
Description
To periodically update the calendar from Network Time Protocol (NTP), use the ntp update-calendar global configuration command. Use the no form of this command to disable the periodic updates.
ntp update-calendarSyntax Description
This command has no arguments or keywords.
Defaults
The calendar is not updated.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.
If a router is synchronized to an outside time source via NTP, it is a good idea to periodically update the calendar with the time learned from NTP. Otherwise, the calendar will tend to gradually lose or gain time. The calendar will be updated only if NTP has synchronized to an authoritative time server.
Examples
The following example configures the system to periodically update the calendar from the system clock:
ntp update-calendar
Related Commands
Manually reads the calendar into the system clock. Sets the calendar from the system clock.
Command
Description
Syntax Description
string Prompt. It can consist of all printing characters and the escape sequences listed in Table 95.
Defaults
The default prompt is either Router or the name defined with the hostname global configuration command, followed by an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode.
Command Modes
Global configuration
Command History
10.3 This command was introduced.
Release
Modification
Usage Guidelines
You can include escape sequences when specifying the prompt. All escape sequences are preceded by a percent sign (%). Table 95 lists the valid escape sequences.
| Escape Sequence | Interpretation |
|---|---|
%h | Host name. This is either Router or the name defined with the hostname global configuration command. |
%n | Physical terminal line (TTY) number of the EXEC user. |
%p | Prompt character itself. It is either an angle bracket (>) for EXEC mode or a pound sign (#) for privileged EXEC mode. |
%s | Space. |
%t | Tab. |
%% | Percent sign (%) |
Issuing the prompt %h command has the same effect as issuing the no prompt command.
Examples
The following example changes the EXEC prompt to include the TTY number, followed by the name and a space:
prompt TTY%n@%h%s%p
The following are examples of user and privileged EXEC prompts that result from the previous command:
TTY17@Router1 > TTY17SRouter1 #
Related Commands
Specifies or modify the host name for the network server.
Command
Description
To guarantee CPU time for processes, use the scheduler allocate global configuration command on the Cisco 7200 series and Cisco 7500 series. The no form of this command restores the default.
scheduler allocate interrupt-time process-time
Syntax Description
interrupt-time Integer (in microseconds) that limits the maximum number of microseconds to spend on fast switching within any one network interrupt context. The range is 400 to 60000 microseconds. The default is 4000 microseconds. process-time Integer (in microseconds) that guarantees the minimum number of microseconds to spend at the process level when network interrupts are disabled. The range is 100 to 4000. The default is 200 microseconds.
Defaults
Approximately 5 percent of the CPU is available for process tasks.
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
This command applies to the Cisco 7200 series and Cisco 7500 series.
|
Caution Cisco recommends that you do not change the default values. |
Examples
The following example makes 20 percent of the CPU available for process tasks:
scheduler allocate 2000 500
Related Commands
Controls the maximum amount of time that can elapse without running system processes.
Command
Description
To control the maximum amount of time that can elapse without running system processes, use the scheduler interval global configuration command. The no form of this command restores the default.
scheduler interval milliseconds
Syntax Description
milliseconds Integer that specifies the interval, in milliseconds. The minimum interval that you can specify is 500 milliseconds; there is no maximum value.
Defaults
High-priority operations are allowed to use as much of the central processor as needed.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The normal operation of the network server allows the switching operations to use as much of the central processor as is required. If the network is running unusually heavy loads that do not allow the processor the time to handle the routing protocols, give priority to the system process scheduler. High-priority operations are allowed to use as much of the central processor as needed.
On the Cisco 7200 series and Cisco 7500 series, use the scheduler allocate global configuration command.
Examples
The following example changes the low-priority process schedule to an interval of 750 milliseconds:
scheduler interval 750
Related Commands
Guarantees CPU time for processes.
Command
Description
To specify that line numbers be displayed and interpreted as decimal numbers rather than octal numbers, use the service decimal-tty global configuration command. Use the no form of this command to restore the default.
service decimal-ttySyntax Description
This command has no arguments or keywords.
Defaults
Decimal numbers on the 500-CS and Cisco 2500 Series.
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Examples
The following example displays decimal rather than octal line numbers:
service decimal-tty
To delay the startup of the EXEC on noisy lines, use the service exec-wait global configuration command. Use the no form of this command to disable the delay function.
service exec-waitSyntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
This command delays startup of the EXEC until the line has been idle (no traffic seen) for 3 seconds. The default is to enable the line immediately on modem activation.
This command is useful on noisy modem lines or when a modem attached to the line is configured to ignore MNP or V.42 negotiations, and MNP or V.42 modems may be dialing in. In these cases, noise or MNP/V.42 packets may be interpreted as usernames and passwords, causing authentication failure before the user gets a chance to type a username/password. The command is not useful on non-modem lines or lines without some kind of login configured.
Examples
The following example delays the startup of the EXEC:
service exec-wait
To allow Finger protocol requests (defined in RFC 742) to be made of the network server, use the service finger global configuration command. This service is equivalent to issuing a remote show users command. Use the no form of this command to remove this service.
service fingerSyntax Description
This command has no arguments or keywords.
Defaults
Enabled
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Examples
The following example disables the Finger protocol:
no service finger
To hide addresses while trying to establish a Telnet session, use the service hide-telnet-address global configuration command. Use the no form of this command to remove this service.
service hide-telnet-addressSyntax Description
This command has no arguments or keywords.
Defaults
Addresses are displayed.
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
The hide feature improves the functionality of the busy-message feature. When you configure only the busy-message command, the normal messages generated during a connection attempt are not displayed; only the busy-message is displayed. When you use the hide and busy features together you can customize the information displayed during Telnet connection attempts. When you configure the service hide-telnet-address command and the busy-message command, the router suppresses the address and displays the message specified with the busy-message command if the connection attempt is not successful.
Examples
The following example hides Telnet addresses:
service hide-telnet-address
Related Commands
busy-message Create a "host failed" message that displays when a connection fails.
Command
Description
To enable the Nagle congestion control algorithm, use the service nagle global configuration command. Use the no form of this command to disable the algorithm.
service nagleSyntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
When using a standard TCP implementation to send keystrokes between machines, TCP tends to send one packet for each keystroke typed. On larger networks, many small packets use up bandwidth and contribute to congestion.
John Nagle's algorithm (RFC 896) helps alleviate the small-packet problem in TCP. In general, it works this way: The first character typed after connection establishment is sent in a single packet, but TCP holds any additional characters typed until the receiver acknowledges the previous packet. Then the second, larger packet is sent, and additional typed characters are saved until the acknowledgment comes back. The effect is to accumulate characters into larger chunks, and pace them out to the network at a rate matching the round-trip time of the given connection. This method is usually a good for all TCP-based traffic. However, do not use the service nagle command if you have XRemote users on X Window sessions.
Examples
The following example enables the Nagle algorithm:
service nagle
To display the configuration prompt (config), use the service prompt config global configuration command. Use the no form of this command to remove the configuration prompt.
service prompt configSyntax Description
This command has no arguments or keywords.
Defaults
The configuration mode prompts (hostname(config)#) appear in all configuration modes.
Command Modes
Global configuration
Command History
11.1 This command was introduced.
Release
Modification
Examples
In the following example, the no service prompt config command prevents the configuration prompt from being displayed. The prompt is still displayed in EXEC mode. When the service prompt config command is entered, the configuration mode prompt reappears.
Router# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)# no service prompt config hostname bob end bob# configure terminal Enter configuration commands, one per line. End with CNTL/Z. service prompt config bob(config)# hostname Router Router(config)# end Router#
Related Commands
Specifies or modify the host name for the network server. Customizes the prompt.
Command
Description
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
11.1 This command was introduced.
Release
Modification
Usage Guidelines
By default, the TCP servers for Echo, Discard, Chargen, and Daytime services are disabled.
When the minor TCP/IP servers are disabled, access to the Echo, Discard, Chargen, and Daytime ports cause the Cisco IOS software to send a TCP RESET packet to the sender and discard the original incoming packet.
|
Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings whether or not you have changed the default using the no service tcp-small-servers command. |
Examples
The following example enables minor TCP/IP services available from the network:
service tcp-small-servers
To set the TCP window to zero (0) when the Telnet connection is idle, use the service telnet-zero-idle global configuration command. Use the no form of this command to disable this service.
service telnet-zero-idleSyntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Normally, data sent to noncurrent Telnet connections is accepted and discarded. When service telnet-zero-idle is enabled, if a session is suspended (that is, some other connection is made active or the EXEC is sitting in command mode), the TCP window is set to zero. This action prevents the remote host from sending any more data until the connection is resumed. Use this command when it is important that all messages sent by the host be seen by the users and the users are likely to use multiple sessions.
Do not use this command if your host will eventually time out and log out a TCP user whose window is zero.
Examples
The following example sets the TCP window to zero when the Telnet connection is idle:
service telnet-zero-idle
Related Commands
resume Switches to another open Telnet, rlogin, LAT, or PAD session.
Command
Description
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
By default the UPD servers for Echo, Discard, and Chargen services are disabled.
When the servers are disabled, access to Echo, Discard, and Chargen ports causes the Cisco IOS software to send an "ICMP port unreachable" message to the sender and discard the original incoming packet.
|
Note Unlike defaults for other commands, this command will display when you perform show running config to display current settings, whether or not you have changed the default using the no service udp-small-servers command. |
Examples
The following example disables minor UDP services on the router:
no service udp-small-servers
To display all alias commands, or the alias commands in a specified mode, use the show aliases EXEC command.
show aliases [mode]
Syntax Description
mode (Optional) Command mode. See Table 94 in the description of the alias command for acceptable options for the mode argument.
Command Modes
EXEC
Command History
10.3 This command was introduced.
Release
Modification
Usage Guidelines
All of the modes listed in Table 94 have their own prompts, except for the null interface mode. For example, the prompt for interface configuration mode is Router(config-if).
Examples
The following is sample output from the show aliases exec commands. The aliases configured for commands in EXEC mode are displayed.
Router# show aliases exec Exec mode aliases: h help lo logout p ping r resume s show w where
Related Commands
Creates a command alias.
Command
Description
To display statistics for the buffer pools on the network server, use the show buffers EXEC command.
show buffers [address hex-addr |[ all | assigned | failures | free | old [dump | header | packet]]
Syntax Description
address (Optional) Displays buffers at a specified address. hex-addr Address, in hexadecimal notation, of the buffer to display. all (Optional) Displays all buffers. assigned (Optional) Displays the buffers in use. failures (Optional) Displays buffer allocation failures. free (Optional) Displays the buffers available for use. old (Optional) Displays buffers older than one minute. input-interface (Optional) Displays interface pool information. If the specified interface-type has its own buffer pool, displays information for that pool. interface-type Value of interface-type can be ethernet, fastethernet, loopback, serial, or null. identifier Identifier of the interface specified in interface-type. pool Displays buffers in a specified buffer pool. pool-name Specifies the name of a buffer pool to use. dump (Optional) Shows the buffer header and all data in the display. header (Optional) Shows the buffer header only in the display. packet (Optional) Shows the buffer header and packet data in the display.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Examples
The following is sample output from the show buffers command with no arguments, showing all buffer pool information:
Router# show buffers
Buffer elements:
398 in free list (500 max allowed)
1266 hits, 0 misses, 0 created
Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50):
50 in free list (20 min, 150 max allowed)
551 hits, 0 misses, 0 trims, 0 created
Middle buffers, 600 bytes (total 25, permanent 25):
25 in free list (10 min, 150 max allowed)
39 hits, 0 misses, 0 trims, 0 created
Big buffers, 1524 bytes (total 50, permanent 50):
49 in free list (5 min, 150 max allowed)
27 hits, 0 misses, 0 trims, 0 created
VeryBig buffers, 4520 bytes (total 10, permanent 10):
10 in free list (0 min, 100 max allowed)
0 hits, 0 misses, 0 trims, 0 created
Large buffers, 5024 bytes (total 0, permanent 0):
0 in free list (0 min, 10 max allowed)
0 hits, 0 misses, 0 trims, 0 created
Huge buffers, 18024 bytes (total 0, permanent 0):
0 in free list (0 min, 4 max allowed)
0 hits, 0 misses, 0 trims, 0 created
Interface buffer pools:
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
Ethernet1 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
Serial0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
Serial1 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
TokenRing0 buffers, 4516 bytes (total 48, permanent 48):
0 in free list (0 min, 48 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
TokenRing1 buffers, 4516 bytes (total 32, permanent 32):
32 in free list (0 min, 48 max allowed)
16 hits, 0 fallbacks
0 failures (0 no memory)
Table 96 describes significant fields shown in the display.
| Field | Description |
|---|---|
Buffer elements | Buffer elements are small structures used as placeholders for buffers in internal operating system queues. Buffer elements are used when a buffer may need to be on more than one queue. |
free list | Total number of the currently unallocated buffer elements. |
max allowed | Maximum number of buffers that are available for allocation. |
hits | Count of successful attempts to allocate a buffer when needed. |
misses | Count of buffer allocation attempts that resulted in growing the buffer pool |
created | Count of new buffers created to satisfy buffer allocation attempts when the available buffers in the pool have already been allocated. |
Public buffer pools: | |
Small buffers | Buffers that are 104 bytes long. |
Middle buffers | Buffers that are 600 bytes long. |
Big buffers | Buffers that are 1524 bytes long. |
VeryBig buffers | Buffers that are 4520 bytes long. |
Large buffers | Buffers that are 5024 bytes long. |
Huge buffers | Buffers that are 18024 bytes long. |
total | Total number of this type of buffer. |
permanent | Number of these buffers that are permanent. |
free list | Number of available or unallocated buffers in that pool. |
min | Minimum number of free or unallocated buffers in the buffer pool |
max allowed | Maximum number of free or unallocated buffers in the buffer pool |
hits | Count of successful attempts to allocate a buffer when needed. |
misses | Count of buffer allocation attempts that resulted in growing the buffer pool in order to allocate a buffer. |
trims | Count of buffers released to the system because they were not being used. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static. |
created | Count of new buffers created in response to misses. This field is displayed only for dynamic buffer pools, not interface buffer pools, which are static. |
Interface buffer pools: | |
total | Total number of this type of buffer. |
permanent | Number of these buffers that are permanent. |
free list | Number of available or unallocated buffers in that pool. |
min | Minimum number of free or unallocated buffers in the buffer pool. |
max allowed | Maximum number of free or unallocated buffers in the buffer pool. |
hits | Count of successful attempts to allocate a buffer when needed. |
fallbacks | Count of buffer allocation attempts that resulted in falling back to the public buffer pool that is the smallest pool at least as big as the interface buffer pool. |
max cache size | Maximum number of buffers from that interface's pool that can be in that interface buffer pool's cache. Each interface buffer pool has its own cache. These are not additional to the permanent buffers; they come from the interface's buffer pools. Some interfaces place all of their buffers from the interface pool into the cache. In this case, it is normal for the free list to display 0. |
failures | Total number of allocation requests that have failed because no buffer was available for allocation; the datagram was lost. Such failures normally occur at interrupt level. |
no memory | Number of failures that occurred because no memory was available to create a new buffer. |
The following is sample output from the show buffers command with an interface type and number:
Router# show buffers Ethernet 0
Ethernet0 buffers, 1524 bytes (total 64, permanent 64):
16 in free list (0 min, 64 max allowed)
48 hits, 0 fallbacks
16 max cache size, 16 in cache
To display the calendar hardware setting, use the show calendar EXEC command:
show calendarSyntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
Some platforms have a calendar which is separate from the system clock. This calendar runs continuously, even if the router is powered off or rebooted.
You can compare the time and date shown with this command with the time and date listed via the show clock command to verify that the calendar and system clock are in sync with each other. The time displayed is relative to the configured time zone.
Examples
In the following sample display, the hardware calendar indicates the timestamp of 12:13:44 p.m. on Friday, July 19, 1996:
Router# show calendar 12:13:44 PST Fri Jul 19 1996
Related Commands
Displays the system clock.
Command
Description
To display the system clock, use the show clock EXEC command.
show clock [detail]
Syntax Description
detail (Optional) Indicates the clock source (NTP, VINES, system calendar, and so forth) and the current summer-time setting (if any).
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The system clock keeps an "authoritative" flag that indicates whether the time is authoritative (believed to be accurate). If the system clock has been set by a timing source (system calendar, NTP, VINES, and so forth), the flag is set. If the time is not authoritative, it will be used only for display purposes. Until the clock is authoritative and the "authoritative" flag is set, the flag prevents peers from synchronizing to the clock when the peers' time is invalid.
The symbol that precedes the show clock display indicates the following:
Symbol | Description |
|---|---|
|
|
|
|
|
|
Examples
The following sample output shows that the current clock is authoritative and that the time source is NTP:
Router# show clock detail 15:29:03.158 PST Mon Mar 3 1997 Time source is NTP
Related Commands
Manually set the system clock. Displays the calendar hardware setting.
Command
Description
To show the status of Network Time Protocol (NTP) associations, use the show ntp associations EXEC command.
show ntp associations [detail]
Syntax Description
detail (Optional) Shows detailed information about each NTP association.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Examples
Detailed descriptions of the information displayed by this command can be found in the NTP specification (RFC 1305).
The following is sample output from the show ntp associations command:
Router# show ntp associations
address ref clock st when poll reach delay offset disp
~172.31.32.2 172.31.32.1 5 29 1024 377 4.2 -8.59 1.6
+~192.168.13.33 192.168.1.111 3 69 128 377 4.1 3.48 2.3
*~192.168.13.57 192.168.1.111 3 32 128 377 7.9 11.18 3.6
* master (synced), # master (unsynced), + selected, - candidate, ~ configured
Table 97 describes significant fields shown in the display.
| Field | Description |
|---|---|
(leading characters in display lines) | The first characters in a display line can be one or more of the following characters: * Synchronized to this peer # Almost synchronized to this peer + Peer selected for possible synchronization - Peer is a candidate for selection ~ Peer is statically configured |
address | Address of peer. |
ref clock | Address of peer's reference clock. |
st | Peer's stratum. |
when | Time since last NTP packet received from peer. |
poll | Polling interval (seconds). |
reach | Peer reachability (bit string, in octal). |
delay | Round-trip delay to peer (milliseconds). |
offset | Relative time of peer's clock to local clock (milliseconds). |
disp | Dispersion |
The following is sample output of the show ntp associations detail command:
Router# show ntp associations detail 172.31.32.2 configured, insane, invalid, stratum 5 ref ID 172.31.32.1, time AFE252C1.6DBDDFF2 (00:12:01.428 PDT Mon Jul 5 1993) our mode active, peer mode active, our poll intvl 1024, peer poll intvl 64 root delay 137.77 msec, root disp 142.75, reach 376, sync dist 215.363 delay 4.23 msec, offset -8.587 msec, dispersion 1.62 precision 2**19, version 3 org time AFE252E2.3AC0E887 (00:12:34.229 PDT Mon Jul 5 1993) rcv time AFE252E2.3D7E464D (00:12:34.240 PDT Mon Jul 5 1993) xmt time AFE25301.6F83E753 (00:13:05.435 PDT Mon Jul 5 1993) filtdelay = 4.23 4.14 2.41 5.95 2.37 2.33 4.26 4.33 filtoffset = -8.59 -8.82 -9.91 -8.42 -10.51 -10.77 -10.13 -10.11 filterror = 0.50 1.48 2.46 3.43 4.41 5.39 6.36 7.34 192.168.13.33 configured, selected, sane, valid, stratum 3 ref ID 192.168.1.111, time AFE24F0E.14283000 (23:56:14.078 PDT Sun Jul 4 1993) our mode client, peer mode server, our poll intvl 128, peer poll intvl 128 root delay 83.72 msec, root disp 217.77, reach 377, sync dist 264.633 delay 4.07 msec, offset 3.483 msec, dispersion 2.33 precision 2**6, version 3 org time AFE252B9.713E9000 (00:11:53.442 PDT Mon Jul 5 1993) rcv time AFE252B9.7124E14A (00:11:53.441 PDT Mon Jul 5 1993) xmt time AFE252B9.6F625195 (00:11:53.435 PDT Mon Jul 5 1993) filtdelay = 6.47 4.07 3.94 3.86 7.31 7.20 9.52 8.71 filtoffset = 3.63 3.48 3.06 2.82 4.51 4.57 4.28 4.59 filterror = 0.00 1.95 3.91 4.88 5.84 6.82 7.80 8.77 192.168.13.57 configured, our_master, sane, valid, stratum 3 ref ID 192.168.1.111, time AFE252DC.1F2B3000 (00:12:28.121 PDT Mon Jul 5 1993) our mode client, peer mode server, our poll intvl 128, peer poll intvl 128 root delay 125.50 msec, root disp 115.80, reach 377, sync dist 186.157 delay 7.86 msec, offset 11.176 msec, dispersion 3.62 precision 2**6, version 2 org time AFE252DE.77C29000 (00:12:30.467 PDT Mon Jul 5 1993) rcv time AFE252DE.7B2AE40B (00:12:30.481 PDT Mon Jul 5 1993) xmt time AFE252DE.6E6D12E4 (00:12:30.431 PDT Mon Jul 5 1993) filtdelay = 49.21 7.86 8.18 8.80 4.30 4.24 7.58 6.42 filtoffset = 11.30 11.18 11.13 11.28 8.91 9.09 9.27 9.57 filterror = 0.00 1.95 3.91 4.88 5.78 6.76 7.74 8.71
Table 98 describes significant fields shown in the display.
| Field | Descriptions |
|---|---|
configured | Peer was statically configured. |
dynamic | Peer was dynamically discovered. |
our_master | Local machine is synchronized to this peer. |
selected | Peer is selected for possible synchronization. |
candidate | Peer is a candidate for selection. |
sane | Peer passes basic sanity checks. |
insane | Peer fails basic sanity checks. |
valid | Peer time is believed to be valid. |
invalid | Peer time is believed to be invalid. |
leap_add | Peer is signaling that a leap second will be added. |
leap-sub | Peer is signaling that a leap second will be subtracted. |
unsynced | Peer is not synchronized to any other machine. |
ref ID | Address of machine peer is synchronized to. |
time | Last timestamp peer received from its master. |
our mode | Our mode relative to peer (active / passive / client / server / bdcast / bdcast client). |
peer mode | Peer's mode relative to us. |
our poll intvl | Our poll interval to peer. |
peer poll intvl | Peer's poll interval to us. |
root delay | Delay along path to root (ultimate stratum 1 time source). |
root disp | Dispersion of path to root. |
reach | Peer reachability (bit string in octal). |
sync dist | Peer synchronization distance. |
delay | Round trip delay to peer. |
offset | Offset of peer clock relative to our clock. |
dispersion | Dispersion of peer clock. |
precision | Precision of peer clock in Hz. |
version | NTP version number that peer is using. |
org time | Originate time stamp. |
rcv time | Receive time stamp. |
xmt time | Transmit time stamp. |
filtdelay | Round trip delay in milliseconds of each sample. |
filtoffset | Clock offset in milliseconds of each sample. |
filterror | Approximate error of each sample. |
Related Commands
Shows the status of Network Time Protocol (NTP).
Command
Description
To show the status of Network Time Protocol (NTP), use the show ntp status EXEC command.
show ntp statusSyntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
10.0 This command was introduced.
Release
Modification
Examples
The following is sample output from the show ntp status command:
Router# show ntp status Clock is synchronized, stratum 4, reference is 192.168.13.57 nominal freq is 250.0000 Hz, actual freq is 249.9990 Hz, precision is 2**19 reference time is AFE2525E.70597B34 (00:10:22.438 PDT Mon Jul 5 1993) clock offset is 7.33 msec, root delay is 133.36 msec root dispersion is 126.28 msec, peer dispersion is 5.98 msec
Table 99 shows the significant fields in the display.
| Field | Description |
|---|---|
synchronized | System is synchronized to an NTP peer. |
unsynchronized | System is not synchronized to any NTP peer. |
stratum | NTP stratum of this system. |
reference | Address of peer we are synchronized to. |
nominal freq | Nominal frequency of system hardware clock. |
actual freq | Measured frequency of system hardware clock. |
precision | Precision of this system's clock (in Hz). |
reference time | Reference timestamp. |
clock offset | Offset of our clock to synchronized peer. |
root delay | Total delay along path to root clock. |
root dispersion | Dispersion of root path. |
peer dispersion | Dispersion of synchronized peer. |
Related Commands
Shows the status of Network Time Protocol (NTP) associations.
Command
Description
Use the show sntp EXEC command on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to show information about the Simple Network Time Protocol (SNTP).
show sntpSyntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
11.2 This command was introduced.
Release
Modification
Examples
The following is sample output from the show sntp command:
Router# show sntp SNTP server Stratum Version Last Receive 171.69.118.9 5 3 00:01:02 172.21.28.34 4 3 00:00:36 Synced Bcast Broadcast client mode is enabled.
Table 100 describes the fields show in this display.
| Field | Description |
|---|---|
SNTP server | Address of the configured or broadcast NTP server. |
Stratum | NTP stratum of the server. The stratum indicates how far away from an authoritative time source the server is. |
Version | NTP version of the server. |
Last Receive | Time since the last NTP packet was received from the server. |
Synced | Indicates the server chosen for synchronization. |
Bcast | Indicates a broadcast server. |
Related Commands
Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the Simple Network Time Protocol (SNTP) to accept Network Time Protocol (NTP) traffic from any broadcast server. Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the Simple Network Time Protocol (SNTP) to request and accept Network Time Protocol (NTP) traffic from a time server.
Command
Description
Use the sntp broadcast client global configuration command to configure a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the Simple Network Time Protocol (SNTP) to accept Network Time Protocol (NTP) traffic from any broadcast server. The no form of the command prevents the router from accepting broadcast traffic.
sntp broadcast clientSyntax Description
This command has no arguments or keywords.
Defaults
The router does not accept SNTP traffic from broadcast servers.
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
SNTP is a compact, client-only version of the Network Time Protocol (NTP). SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.
SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.
You must configure the router with either this command or the sntp server command in order enable SNTP.
Examples
The following example enables the router to accept broadcast NTP packets and shows sample show sntp command output:
Router(config)# sntp broadcast client Router(config)# end Router# %SYS-5-CONFIG: Configured from console by console Router# show sntp SNTP server Stratum Version Last Receive 172.21.28.34 4 3 00:00:36 Synced Bcast Broadcast client mode is enabled.
Related Commands
Shows information about the Simple Network Time Protocol (SNTP) on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router. Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the Simple Network Time Protocol (SNTP) to request and accept Network Time Protocol (NTP) traffic from a time server.
Command
Description
Use the sntp server global configuration command to configure a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1720, or Cisco 800 router to use the Simple Network Time Protocol (SNTP) to request and accept Network Time Protocol (NTP) traffic from a stratum 1 time server. The no form of the command removes a server from the list of NTP servers.
sntp server {address | hostname} [version number]
Syntax Description
address IP address of the time server. hostname Hostname of the time server. version number (Optional) Version of NTP to use. The default is 1.
Defaults
The router does not accept SNTP traffic from a time server.
Command Modes
Global configuration
Command History
11.2 This command was introduced.
Release
Modification
Usage Guidelines
SNTP is a compact, client-only version of the Network Time Protocol (NTP). SNMP can only receive the time from NTP servers; it cannot be used to provide time services to other systems.
SNTP typically provides time within 100 milliseconds of the accurate time, but it does not provide the complex filtering and statistical mechanisms of NTP. In addition, SNTP does not authenticate traffic, although you can configure extended access lists to provide some protection.
Enter this command once for each NTP server.
You must configure the router with either this command or the sntp broadcast client command in order enable SNTP.
SNTP time servers should operate only at the root (stratum 1) of the subnet, and then only in configurations where no other source of synchronization other than a reliable radio or modem time service is available. A stratum 2 server cannot be used as an SNTP time server. The use of SNTP rather than NTP in primary servers should be carefully considered.
Examples
The following example enables the router to request and accept NTP packets from the server at 172.21.118.9 and shows sample show sntp command output:
Router(config)# sntp server 172.21.118.9 Router(config)# end Router# %SYS-5-CONFIG: Configured from console by console Router# show sntp SNTP server Stratum Version Last Receive 172.21.118.9 5 3 00:01:02 Synced
Related Commands
Shows information about the Simple Network Time Protocol (SNTP) on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router. Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the Simple Network Time Protocol (SNTP) to accept Network Time Protocol (NTP) traffic from any broadcast server.
Command
Description
Posted: Wed Aug 16 20:43:16 PDT 2000
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