Basic System Management Commands

Syntax Description

start time date

(Optional) Absolute time and date that the associated permit or deny statement starts going into effect. The time is expressed in a 24-hour clock, in the form of hours:minutes. For example, 8:00 is 8:00 am and 20:00 is 8:00 pm. The date is expressed in the format day month year. The minimum start is 00:00 1 January 1993. If no start time and date are specified, the permit or deny statement is in effect immediately.

end time date

(Optional) Absolute time and date that the associated permit or deny statement is no longer in effect. Same time and date format as described for the start. The end time and date must be after the start time and date. The maximum end time is 23:59 31 December 2035. If no end time and date are specified, the permit or deny statement is in effect indefinitely.

Defaults

There is no absolute time when the time range is in effect.

Command Modes

Time-range configuration

Command History

Release	Modification
12.0(1)T	This command was introduced.

Usage Guidelines

For Cisco IOS Release 12.1, IP and IPX extended access lists are the only functions that can use time ranges. For further information on using these functions, see the Cisco IOS 12.1 IP and IP Routing and the Cisco IOS 12.1 AppleTalk and Novell IPX publications.

The absolute command is one way to specify when a time range is in effect. Another way is to specify a periodic length of time with the periodic command. Use either of these commands after the time-range command, which enables time-range configuration mode and specifies a name for the time range. Only one absolute entry is allowed per time-range command.

If a time-range command has both absolute and periodic values specified, then the periodic items are evaluated only after the absolute start time is reached, and are not further evaluated after the absolute end time is reached.

Note   All time specifications are taken as local time. To ensure that the time range entries take effect at the desired times, the system clock should be synchronized. Use NTP or the hardware calendar to synchronize the clock. For more information, refer to the "Performing Basic System Management" chapter of the Cisco IOS Configuration Fundamentals Configuration Guide.

Examples

The following example configures an access list named northeast, which references a time range named xyz. The access list and time range together permit traffic on Ethernet interface 0 starting at noon on January 1, 2001 and going forever.

time-range xyz
 absolute start 12:00 1 January 2001
!
ip access-list extended northeast
 permit ip any any time-range xyz
!
interface ethernet 0
 ip access-group northeast in
 

The following example permits UDP traffic until noon on December 31, 2000. After that time, UDP traffic is no longer allowed out Ethernet interface 0.

time-range abc
 absolute end 12:00 31 December 2000
!
ip access-list extended northeast
 permit udp any any time-range abc
!
interface ethernet 0
 ip access-group northeast out
 

The following example permits UDP traffic out Ethernet interface 0 on weekends only, from 8:00 a.m. on January 1, 1999 to 6:00 p.m. on December 31, 2001:

time-range test
 absolute start 8:00 1 January 1999 end 18:00 31 December 2001
 periodic weekends 00:00 to 23:59
!
ip access-list extended northeast
 permit udp any any time-range test
!
interface ethernet 0
 ip access-group northeast out

Related Commands

Command	Description
deny	Sets conditions under which a packet does not pass a named access list.
periodic	Specifies a recurring (weekly) start and end time for a time-range.
permit	Sets conditions under which a packet passes a named access list.
time-range	Enables time-range configuration mode and names a time-range definition.

Syntax Description

mode	Command mode of the original and alias commands. See Table 104 for a list of options for this argument.
alias-name	Command alias.
alias-command-line	Original command syntax.

Defaults

Command Modes

Global configuration

Command History

Release	Modification
10.3	This command was introduced.

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.

See the summary of command modes in the "Using the Command-Line Interface" chapter in the Cisco IOS 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

Command	Description
show aliases	Displays all alias commands.

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. A maximum of 20,480 small buffers can be constructed in the 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.

Defaults

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

buffers small min-free 50
 

The following example increases the permanent buffer pool allocation for big buffers to 200:

buffers big permanent 200

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

Command	Description
load-interval	Changes the length of time for which data is used to compute load statistics.
show buffers	Displays statistics for the buffer pools on the network server.

Syntax Description

number

Huge buffer size, in bytes.

Defaults

18024 bytes

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
buffers	Makes adjustments to initial buffer pool settings and to the limits at which temporary buffers are created and destroyed.
show buffers	Displays statistics for the buffer pools on the network server.

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

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Syntax Description

This command has no arguments or keywords.

Defaults

The router is not configured as a time source.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
ntp master	Configures the Cisco IOS software as an 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.

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
calendar set	Sets the system calendar.
clock read-calendar	Manually reads the calendar into the system clock.
clock summer-time	Configures the system to automatically switch to summer time (daylight savings time).
clock timezone	Sets the time zone for display purposes.

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	(Optional) Week of the month (1 to 5 or last).
day	(Optional) Day of the week (Sunday, Monday,...).
date	Date of the month (1 to 31).
month	(Optional) Month (January, February,...).
year	Year (1993 to 2035).
hh:mm	(Optional) 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

Release	Modification
10.0	This command was introduced.

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

Command	Description
calendar set	Sets the system calendar.
clock timezone	Sets the time zone for display purposes.

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
calendar set	Sets the system calendar.
clock set	Manually set the system clock.
clock summer-time	Configures the system to automatically switch to summer time (daylight savings time).
show clock	Displays the system clock.

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
clock read-calendar	Manually reads the calendar into the system clock.
ntp update-calendar	Periodically updates the calendar from NTP.

Syntax Description

version

Cisco IOS Release number, not earlier than 10.2.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
11.1	This command was introduced.

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

Command	Description
access-list (extended)	Provides extended access lists that allow more detailed access lists.
access-list (standard)	Defines a standard XNS access list.

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

Release	Modification
10.0	This command was introduced.

Usage Guidelines

The order of display at startup is banner message-of-the-day (MOTD), then login and password prompts, then EXEC banner.

Examples

The following example changes the host name to sandbox:

hostname sandbox

Related Commands

Command	Description
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.

Syntax Description

This command has no arguments or keywords.

Defaults

Enabled

Command Modes

Global configuration

Command History

Release	Modification
11.2	This command was introduced.

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
 

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

Release	Modification
11.1	This command was introduced.

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

Command	Description
ip radius source-interface	Forces RADIUS to use the IP address of a specified interface for all outgoing RADIUS packets.

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

Release	Modification
11.1	This command was introduced.

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

Command	Description
ip radius source-interface	Forces RADIUS to use the IP address of a specified interface for all outgoing RADIUS packets.

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

Release	Modification
10.3	This command was introduced.

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

Command	Description
show interfaces	Displays ALC information.

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
access-list	Configures the access list mechanism for filtering frames by protocol type or vendor code.

Syntax Description

This command has no arguments or keywords.

Defaults

No authentication

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Syntax Description

number	Key number (1 to 4294967295).
md5	Authentication key. Message authentication support is provided using the message digest algorithm 5(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

Release	Modification
10.0	This command was introduced.

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

Command	Description
ntp authenticate	Enables NTP authentication.
ntp peer	Configures the system clock to synchronize a peer or to be synchronized by a peer.
ntp server	Allows the system clock to be synchronized by a time server.
ntp trusted-key	Authenticates the identity of a system to which NTP will synchronize.

Syntax Description

version number

(Optional) Number from 1 to 3 indicating the NTP version.

Defaults

Disabled

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following example configures Ethernet interface 0 to send NTP version 2 packets:

interface ethernet 0
 ntp broadcast version 2

Related Commands

Command	Description
ntp broadcast client	Allows the system to receive NTP broadcast packets on an interface.
ntp broadcastdelay	Sets the estimated round-trip delay between the Cisco IOS software and an NTP broadcast server.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
ntp broadcast	Specifies that a specific interface should send NTP broadcast packets.
ntp broadcastdelay	Sets the estimated round-trip delay between the Cisco IOS software and an NTP broadcast server.

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
ntp broadcast	Specifies that a specific interface should send NTP broadcast packets.
ntp broadcast client	Allows the system to receive NTP broadcast packets on an interface.

Syntax Description

value

Amount to add to the system clock for each clock hardware tick (in units of 2 to 32 seconds).

Defaults

17179869 2-32 seconds (4 milliseconds)

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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.

Syntax Description

This command has no arguments or keywords.

Defaults

Enabled

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

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

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
clock calendar-valid	Configures a router as a time source for a network based on its calendar.

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
ntp authentication-key	Defines an authentication key for NTP.
ntp server	Allows the system clock to be synchronized by a time server.
ntp source	Uses a particular source address in NTP packets.

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

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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

Command	Description
ntp authentication-key	Defines an authentication key for NTP.
ntp peer	Configures the system clock to synchronize a peer or to be synchronized by a peer.
ntp source	Uses a particular source address in NTP packets.

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

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Syntax Description

key-number

Key number of authentication key to be trusted.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Syntax Description

This command has no arguments or keywords.

Defaults

The calendar is not updated.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Some platforms have a battery-powered system calendar in addition to the software based system clock. The system calendar runs continuously, even if the router is powered off or rebooted.

If the system clock is synchronized to an outside time source via NTP, it is a good idea to periodically update the system calendar with the time learned from NTP. Otherwise, the calendar will tend to gradually lose or gain time, and the clock and calendar may become out of sync with each other. The ntp update-calendar command will enable the system calendar to be periodically updated with the time specified by the NTP source. The calendar will be updated only if NTP has synchronized to an authoritative time server.

Many lower-end routers (for example, the Cisco 2500 series or the Cisco 2600 series) do not have system calendars, so this command is not available on those platforms.

To force a single update of the system calendar from the system clock, use the clock update-calendar command.

Examples

The following example configures the system to periodically update the calendar from the NTP time-source:

Router(config)# ntp update-calendar

Related Commands

Command	Description
clock read-calendar	Manually reads the calendar into the system clock.
clock update-calendar	Sets the calendar from the system clock.

Syntax Description

days-of-the-week

The first occurrence of this argument is the starting day or days that the associated time range is in effect. The second occurrence is the ending day or days the associated statement is in effect. This argument can be any single day or combinations of days: Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday. Other possible values are: daily — Monday through Sunday weekdays — Monday through Friday weekend — Saturday and Sunday If the ending days of the week are the same as the starting days of the week, they can be omitted.

hh:mm

The first occurrence of this argument is the starting hours:minutes that the associated time range is in effect. The second occurrence is the ending hours:minutes the associated statement is in effect. The hours:minutes are expressed in a 24-hour clock. For example, 8:00 is 8:00 a.m. and 20:00 is 8:00 p.m.

Defaults

No recurring time range is defined.

Command Modes

Time-range configuration

Command History

Release	Modification
12.0(1)T	This command was introduced.

Usage Guidelines

Note   For Cisco IOS Release 12.1, IP and IPX extended access lists are the only functions that can use time ranges. For further information on using these functions, see the Cisco IOS 12.1 IP and IP Routing and the Cisco IOS 12.1 AppleTalk and Novell IPX publications.

The periodic command is one way to specify when a time range is in effect. Another way is to specify an absolute time period with the absolute command. Use either of these commands after the time-range command, which specifies the name of the time range. Multiple periodic entries are allowed per time-range command.

If the end days-of-the-week are the same as the start, they can be omitted.

If a time-range command has both absolute and periodic values specified, then the periodic items are evaluated only after the absolute start time is reached, and are not further evaluated after the absolute end time is reached.

Note   All time specifications are taken as local time. To ensure that the time range entries take effect at the desired times, you should synchronize the system clock, using NTP or the hardware calendar.

Here are some typical settings for your convenience:

If you want:	Configure this:
Monday through Friday, 8:00 a.m. to 6:00 p.m. only	periodic weekday 8:00 to 18:00
Every day of the week, from 8:00 a.m. to 6:00 p.m. only	periodic daily 8:00 to 18:00
Every minute from Monday 8:00 a.m. to Friday 8:00 p.m.	periodic monday 8:00 to friday 20:00
All weekend, from Saturday morning through Sunday night	periodic weekend 00:00 to 23:59
Saturdays and Sundays, from noon to midnight.	periodic weekend 12:00 to 23:59

Examples

The following example denies HTTP traffic on Monday through Friday between the hours of 8:00 a.m. and 6:00 p.m.:

time-range no-http
 periodic weekdays 8:00 to 18:00
!
ip access-list extended strict
 deny tcp any any eq http time-range no-http
!
interface ethernet 0
 ip access-group strict in
 

The following example permits Telnet traffic on Mondays, Tuesdays, and Fridays between the hours of 9:00 a.m. and 5:00 p.m.:

time-range testing
 periodic Monday Tuesday Friday 9:00 to 17:00
!
ip access-list extended legal
 permit tcp any any eq telnet time-range testing
!
interface ethernet 0
 ip access-group legal in

Related Commands

Command	Description
absolute	Specifies an absolute start and end time for a time-range.
access-list (extended)	Defines an extended IP access list.
deny (IP)	Sets conditions under which a packet does not pass a named IP access list.
permit (IP)	Sets conditions under which a packet passes a named IP access list.
time-range	Enables time-range configuration mode and names a time-range definition.

Syntax Description

string

Prompt. It can consist of all printing characters and the escape sequences listed in Table 105.

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

Release	Modification
10.3	This command was introduced.

Usage Guidelines

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

Command	Description
hostname	Specifies or modifies the host name for the network server.

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

Release	Modification
11.2	This command was introduced.

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

Command	Description
scheduler interval	Controls the maximum amount of time that can elapse without running system processes.

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

Release	Modification
10.0	This command was introduced.

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

Command	Description
scheduler allocate	Guarantees CPU time for processes.

Syntax Description

This command has no arguments or keywords.

Defaults

Decimal numbers on the 500-CS and Cisco 2500 Series routers.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following example displays decimal rather than octal line numbers:

service decimal-tty

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Syntax Description

This command has no arguments or keywords.

Defaults

Enabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following example disables the Finger protocol:

no service finger

Syntax Description

This command has no arguments or keywords.

Defaults

Addresses are displayed.

Command Modes

Global configuration

Command History

Release	Modification
11.2	This command was introduced.

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

Command	Description
busy-message	Creates a "host failed" message that displays when a connection fails.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Syntax 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

Release	Modification
11.1	This command was introduced.

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

Command	Description
hostname	Specifies or modifies the host name for the network server.
prompt	Customizes the prompt.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
11.1	This command was introduced.

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

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
resume	Switches to another open Telnet, rlogin, LAT, or PAD session.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
11.2	This command was introduced.

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

Syntax Description

mode	(Optional) Command mode. See Table 104 in the description of the alias command for acceptable options for the mode argument.

Command Modes

EXEC

Command History

Release	Modification
10.3	This command was introduced.

Usage Guidelines

All of the modes listed in Table 102 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

Command	Description
alias	Creates a command alias.

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.
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.
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	(Optional) Displays buffers in a specified buffer pool.
pool-name	Specifies the name of a buffer pool to use.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

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)
 

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
 

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

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

Command	Description
show clock	Displays the system clock.

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

Release	Modification
10.0	This command was introduced.

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
*	Time is not authoritative.
(blank)	Time is authoritative.
.	Time is authoritative, but NTP is not synchronized.

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

Command	Description
clock set	Manually sets the system clock.
show calendar	Displays the calendar hardware setting.

Syntax Description

detail

(Optional) Shows detailed information about each NTP association.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

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
 

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   
 

Related Commands

Command	Description
show ntp status	Shows the status of NTP.

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

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
 

Related Commands

Command	Description
show ntp associations	Shows the status of NTP associations.

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
11.2	This command was introduced.

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.
 

Related Commands

Command	Description
sntp broadcast client	Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the SNTP to accept NTP traffic from any broadcast server.
sntp server	Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the SNTP to request and accept NTP traffic from a time server.

Syntax 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

Release	Modification
11.2	This command was introduced.

Usage Guidelines

SNTP is a compact, client-only version of the 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.

Syntax Description

address	IP address of the time server.
hostname	Host name 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

Release	Modification
11.2	This command was introduced.

Usage Guidelines

SNTP is a compact, client-only version of the 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

Command	Description
show sntp	Shows information about the SNTP on a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router.
sntp broadcast client	Configures a Cisco 1003, Cisco 1004, Cisco 1005, Cisco 1600, Cisco 1720, or Cisco 1750 router to use the SNTP to accept NTP traffic from any broadcast server.

Syntax Description

time-range-name

Desired name for the time range. The name cannot contain a space or quotation mark, and must begin with a letter.

Defaults

None

Command Modes

Global configuration

Command History

Release	Modification
12.0(1)T	This command was introduced.

Usage Guidelines

The time-range entries are identified by a name, which is referred to by one or more other configuration commands. Multiple time ranges can occur in a single access list or other feature.

Note   For Cisco IOS Release 12.1, IP and IPX extended access lists are the only functions that can use time-ranges. For further information on using these functions, see the Cisco IOS 12.1 IP and IP Routing and the Cisco IOS 12.1 AppleTalk and Novell IPX publications.

After the time-range command, use the periodic command, the absolute command, or some combination of them to define when the feature is in effect. Multiple periodic commands are allowed in a time range; only one absolute command is allowed.

Tips To avoid confusion, use different names for time ranges and named access lists.

Examples

The following example denies HTTP traffic on Monday through Friday between the hours of 8:00 a.m. and 6:00 p.m. The example allows UDP traffic on Saturday and Sunday from noon to midnight only.

time-range no-http
 periodic weekdays 8:00 to 18:00
!
time-range udp-yes
 periodic weekend 12:00 to 24:00
!
ip access-list extended strict
 deny tcp any any eq http time-range no-http
 permit udp any any time-range udp-yes
!
interface ethernet 0
 ip access-group strict in

Related Commands

Command	Description
absolute	Specifies an absolute start and end time for a time range.
ip access-list	Defines an IP access list by name.
periodic	Specifies a recurring (weekly) start and end time for a time range.
permit (IP)	Sets conditions under which a packet passes a named IP access list.