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This appendix provides a command reference for those Cisco IOS commands—or aspects of the commands—that are unique to Server Load Balancing (SLB) and Layer 3 switching. All other commands used with this feature are documented in the Cisco IOS Release 12.0 and 12.0(5)T command reference publications.
Server load balancing (SLB) allows you to define a virtual server that represents a group of real servers in a cluster of network servers known as a server farm.The clients are configured to connect to the IP address of the virtual server. When a client initiates a connection to the virtual server, the IOS SLB function chooses a real server for the connection based on a configured load balancing algorithm. The following commands let you set up and monitor SLB.
To control the installation of a static route to the Null0 interface for a virtual server address, use the advertise virtual server configuration command. Advertisement of this static route using the routing protocol requires that you configure redistribution of static routes for the routing protocol. To prevent the installation of a static route for the virtual server IP address, use the no form of this command.
advertiseSyntax Description
This command has no arguments or keywords.
Defaults
The virtual server IP address is added to the routing table.
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example prevents advertisement of the virtual server's IP address in routing protocol updates:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# no advertise
Related Commands
Displays information about the virtual servers.
Command
Description
To configure a DFP agent, use the agent DFP configuration command. To remove an agent definition from the DFP configuration, use the no form of this command.
agent ip-address port [timeout [retry_count [retry_interval]]]
Syntax Description
ip-address Agent IP address. port Configures the agent port number. The valid range is 1 to 65535. timeout (Optional) Time period, in seconds, during which the DFP manager must receive an update from the DFP agent. retry_count (Optional) Number of times DFP manager attempts to establish the TCP connection to the DFP agent. retry_interval (Optional) Interval, in seconds, between retries.
Defaults
Timeout default: 0 seconds (no timeout)
Retry_count default: 0 (infinite retries)
Retry_interval default: 180 seconds
Command Modes
DFP configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
You can configure up to 1024 agents.
A DFP agent collects status information about a server's load capability and reports that information to a load manager. The DFP agent might reside on the server, or it might be a separate device that collects and consolidates the information from several servers before reporting to the load manager.
Examples
The following example configures a DFP agent:
SLB-Switch(config)# ip slb dfp SLB-Switch(config-slb-dfp)# agent 17.17.17.17 4321
Related Commands
Configures the IOS SLB DFP.
Command
Description
To configure a bind ID, use the bindid server farm configuration command. To remove a bind ID from the server farm configuration, use the no form of this command.
bindid [bind_id]
Syntax Description
bind_id (Optional) Bind ID number.
Defaults
Bind_id default: 0
Command Modes
Server farm configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
You can configure one bind ID on each bindid command.
The bind ID allows a single physical server to be bound to multiple virtual servers and report a different weight for each one. Thus, the single real server is represented as multiple instances of itself, each having a different bind ID. DFP uses the bind ID to identify which instance of the real server a given weight is for.
Examples
The following example configures bind ID 309:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# bindid 309
Related Commands
Configures the IOS SLB DFP. Displays information about the server farm configuration.
Command
Description
To clear IP SLB connections or counters, use the clear ip slb command.
clear ip slb {connections [serverfarm farm_name | vserver server_name] | counters}
Syntax Description
connections Clears the IP SLB connection database. serverfarm Clears the connection database for the serverfarm named. farm_name Character string used to identify the serverfarm. vserver Clears the connection database for the virtual server named. server_name Character string used to identify the virtual server. counters Clears the IP SLB counters.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example clears the connection database of server farm FARM1:
SLB-Switch# clear ip slb connections serverfarm FARM1
The following example clears the connection database of virtual server VSERVER1:
SLB-Switch# clear ip slb connections vserver VSERVER1
The following example clears the SLB counters:
SLB-Switch# clear ip slb counters
Related Commands
Displays information about the SLB server farms. Displays information about the SLB virtual servers. Displays information about the SLB connections.
Command
Description
To define which clients are allowed to use the virtual server, use the client virtual server configuration command. You can use more than one client command to define more than one client. To remove a client definition from the IOS SLB configuration, use the no form of this command.
client ip-address network-mask
Syntax Description
ip-address Client IP address. network-mask Client IP network mask.
Defaults
Ip_address default: 0.0.0.0 (all clients)
Network_mask default: 0.0.0.0 (all subnetworks)
Taken together, the default is client 0.0.0.0 0.0.0.0 (allow all clients on all subnetworks to use the virtual server).
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
The network-mask value is applied to the source IP address of incoming connections. The result must match the ip-address value for the client to be allowed to use the virtual server.
Examples
The following example allows only clients from 10.4.4.x access to the virtual server:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# client 10.4.4.0 255.255.255.0
Related Commands
Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To configure basic authentication values for the HTTP SLB probe, use the credentials configuration command. To remove a credentials configuration, use the no form of this command.
credentials {username} [password]
Syntax Description
username Configures the authentication username of the HTTP probe header. The character string is limited to 15 characters. password Configures the authentication password of the HTTP probe header. The character string is limited to 15 characters.
Defaults
No default behavior or values.
Command Modes
HTTP probe configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example configures an HTTP probe named DOGULA changing the CLI to HTTP SLB probe submode, configures the HTTP authentication to username, chris and configures the password as develop:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# credentials chris develop
Related Commands
Displays the SLB HTTP probe configuration.
Command
Description
To display debug messages for IOS SLB, use the debug ip slb EXEC command. To stop debug output, use the no form of this command.
debug ip slb {conns | dfp | icmp | natpool | reals | replication | all}
Syntax Description
all Displays all debug messages for IOS SLB. conns Displays debug messages for all connections being handled by IOS SLB. dfp Displays debug messages for the IOS SLB DFP and DFP agents. icmp Displays all Internet Control Message Protocol debug messages for IOS SLB. natpool Displays debug messages related to the SLB client NAT pool. reals Displays debug messages for all real servers defined to IOS SLB. replication Displays debug messages related to SLB stateful backup virtual server.
Defaults
No default behavior or values.
Command Modes
EXEC configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
See the following caution before using debug commands:
 |
Caution Because debugging output is assigned high priority in the CPU process, it can render the system unusable. For this reason, only use debug commands to troubleshoot specific problems or during troubleshooting sessions with Cisco technical support staff. Moreover, it is best to use debug commands during periods of lower network traffic and fewer users. Debugging during these periods reduces the effect these commands have on other users on the system. |
Examples
The following example configures a debug session to check all IP SLB parameters:
SLB-Switch# debug ip slb all
SLB All debugging is on
SLB-Switch#
The following example stops all debugging:
SLB-Switch# no debug all
All possible debugging has been turned off
SLB-Switch#
The following example configures debugging to check IP SLB replication used with the stateful backup feature and displays the output from the send or transmit virtual server:
SLB-Switch# debug ip slb replication *Mar 2 08:02:38.019: SLB Replicate: (send) update vs: VS1 update_count 42
The following example configures debugging to check IP SLB replication used with the stateful backup feature and displays the output from the receive virtual server:
SLB-Switch# debug ip slb replication 01:32:53: SLB Replicate: (rcvd) update vs: VS1 01:32:53: vserver prot client real state mode ------------------------------------------------------------------------------- 01:32:53: VS1 TCP 20.20.30.60:34819 20.20.20.10:0 FINSERVE3600 01:32:53: VS1 TCP 20.20.30.60:34819 20.20.20.10:0 CLOSING 10 01:32:53: VS1 TCP 20.20.30.60:35332 20.20.20.10:0 FINSERVE3600
The following example shows IOS SLB DFP debug output:
SLB-Switch# debug ip slb dfp SLB DFP debugging is on SLB-Switch#
To change the amount of time IOS SLB maintains TCP connection context after a connection has terminated, use the delay virtual server configuration command. To restore the default delay timer, use the no form of this command.
delay duration
Syntax Description
duration Delay timer duration in seconds. The valid range is 1 to 600 seconds. The default value is 10 seconds.
Defaults
Duration default: 10 seconds
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example specifies that IOS SLB maintains TCP connection context for 30 seconds after a connection has terminated:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# delay 30
Related Commands
Configures the virtual server attributes. Displays the configuration of the virtual server.
Command
Description
To configure a status code to expect from the HTTP probe, use the expect configuration command. To remove a status code configuration, use the no form of this command.
expect status number
Syntax Description
number Configures the expected HTTP status code within the range 100-599.
Defaults
No default expected status code is 4XX.
Command Modes
HTTP probe configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
The expect command configures the expected status code to be received from the servers. Any other status number or if the server fails to respond the real server is considered failed and taken out of service.
Examples
The following example configures an HTTP probe named DOGULA. Changing the CLI to HTTP submode configures the HTTP probe to expect the status code 40l:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# expect status 401
Related Commands
Configures the IP SLB probe name. Displays the SLB HTTP probe configuration.
Command
Description
To specify the conditions that indicate a server failure, use the faildetect real server configuration command. To restore the default values that indicate a server failure, use the no form of this command.
faildetect numconns number-conns [numclients number-clients]
Syntax Description
numconns Number of consecutive TCP connection reassignments allowed before a real server is considered to have failed. number-conns Connection reassignment threshold value in the range from 1 to 255. numclients (Optional) Number of unique client connection failures, which, together with the server connection reassignment threshold, constitutes failure of a real server. number-clients (Optional) Client connection reassignment threshold value in the range from 1 to 8.
Defaults
If the faildetect command is not specified, the default value of the connection reassignment threshold is 8.
If the numclients keyword is not specified, the default value of the unique client failure threshold is whichever value is less, number-conns or 8.
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
In the following example the connection reassignment threshold is set to 16 and, because the number-clients keyword is not configured, the threshold for unique client connection failure is set to the default value 8. The real server is considered to have failed when 8 unique clients have had connection failure and there have been 16 connection reassignments.
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 SLB-Switch(config-slb-real)# faildetect numconns 16
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
To configure the basic authentication values for the HTTP probe, use the header HTTP probe configuration command. To remove a header HTTP probe configuration, use the no form of this command.
header {field-name}
Syntax Description
field-name Configures the name of the HTTP probe header. The character string is limited to 15 characters.
Defaults
No default behavior or values.
Command Modes
HTTP probe configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
The header HTTP probe command configures authentication parameters of the CGI header.
The following headers are inserted in the server CGI script by default:
Accept: */* Connection: close User-Agent: cisco-slb-probe/1.0 Host: virtual IP address
 |
Note The colon ( : ) separating the field-name and field-value is automatically inserted if not provided. Multiple headers with the same name are not allowed. |
Examples
The following example configures an HTTP probe named DOGULA changing the CLI to HTTP submode and configures HTTP probe header name as Cookie:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# header Cookie
Related Commands
Configures the IP SLB probe name. Displays an SLB HTTP probe configuration.
Command
Description
To specify the minimum amount of time IOS SLB maintains connection information in the absence of packet activity for a connection, use the idle virtual server configuration command. To restore the default idle duration value, use the no form of this command.
idle duration
Syntax Description
duration Idle connection timer duration in seconds. Valid values range from 10 to 65535.
Defaults
Duration default: 3600 seconds
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example instructs IOS SLB to maintain connection information for 120 seconds on an idle connection.
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# idle 120
Related Commands
Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To enable the real server for use by IOS SLB, use the inservice real server configuration command. To remove the real server from service, use the no form of this command.
inserviceSyntax Description
This command has no arguments or keywords.
Defaults
If the inservice command is not specified, the real server is defined to IOS SLB but is not used.
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example enables the real server for use by the IOS SLB feature:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 SLB-Switch(config-slb-real)# inservice
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
To enable the virtual server for use by IOS SLB, use the inservice virtual server configuration command. To remove the virtual server from service, use the no form of this command.
inservice [standby group-name]
Syntax Description
standby (Optional) Configures the HSRP standby virtual server. groupname (Optional) Specifies the HSRP group name with which the SLB virtual server is associated.
Defaults
If the inservice command is not specified, the virtual server is defined to IOS SLB but is not used.
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example enables the real server for use by the IOS SLB feature:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# inservice
Related Commands
Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To configure a HTTP probe interval, use the interval configuration command. To remove an HTTP probe interval configuration, use the no form of this command.
interval seconds
Syntax Description
seconds Designates the number of seconds to wait before reattempting the probe. Valid values range from 1-65535 seconds.
Defaults
The default interval value is 8 seconds.
Command Modes
HTTP probe configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example configures an HTTP probe named DOGULA changing the CLI to HTTP submode, configures the HTTP probe timer interval to transmit every 11 seconds, and confirms the status of the server:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# interval 11
Related Commands
Displays an SLB HTTP probe configuration.
Command
Description
To configure DFP and supply an optional password, use the ip slb dfp global configuration command. To remove the DFP configuration, use the no form of this command.
ip slb dfp [password password [timeout]]
Syntax Description
password (Optional) Specifies a password for MD5 authentication. password (Optional) Password value for MD5 authentication. This password must match the password configured on the host agent. timeout (Optional) Delay period, in seconds, during which both the old password and the new password are accepted.
Defaults
Timeout default: 180 seconds
Command Modes
Global configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
The optional password, if configured, must match the password configured on the host agent.
The timeout options allow you to change the password without stopping messages between the agent and the manager.
Examples
The following example configures DFP, sets the password to flounder, configures a timeout period of 60 seconds, and changes to DFP agent configuration mode:
SLB-Switch(config)# ip slb dfp flounder 60 SLB-Switch(config-slb-dfp)#
Related Commands
Configures a DFP agent.
Command
Description
To configure a SLB NAT, you must create at least one client address pool, use the ip slb natpool configuration command. To remove an ip slb natpool configuration, use the no form of this command.
ip slb natpool pool-name start-ip end-ip netmask mask
Syntax Description
pool-name Configures a character string used to identify this client address pool. The character string is limited to 15 characters. start-ip Configures a starting IP address that defines the range of addresses in the address pool. end-ip Configures an ending IP address that defines the range of addresses in the address pool. netmask Keyword used to configure the subnet mask. mask Mask for the associated IP subnet.
Defaults
None
Command Modes
Global configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
If you want client network address translation, you must create at least one client address pool.
Examples
The following example configures an SLB NAT server farm pool of addresses with the name web-clients, the IP address range from 128.3.0.1 through 128.3.0.254, and a subnet mask of 255.255.0.0:
SLB-Switch(config)# ip slb natpool web-clients 128.3.0.1 128.3.0.254 netmask 255.255.0.0
Related Commands
Displays information about the server farm configuration.
Command
Description
To configure a HTTP probe name and to change to HTTP probe configuration submode, use the ip slb probe configuration command.
To remove an ip slb probe configuration, use the no form of this command.
ip slb probe name http [url path]
Syntax Description
name Configures a name for the HTTP probe. The character string is limited to 15 characters. path Configures the default path to the CGI server.
Defaults
If no URL path is configured, the default is /.
Command Modes
Global configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
This command configures the HTTP probe name and configures the path to the HTTP CGI server. If no path is configured, the default is /. The ip slb probe command also changes the user interface to HTTP submode.
The HTTP probe cannot be unconfigured while it is being used by the server farm.
Only one HTTP probe can be configured per server farm.
Examples
The following example configures an SLB probe with the DOGULA, sets the server path to /probe.cgi?all, then changes to HTTP configuration submode:
SLB-Switch(config)# ip slb probe DOGULA http /probe.cgi?all SLB-Switch(config-slb-probe)#
Related Commands
Displays an SLB HTTP probe configuration.
Command
Description
To identify a server farm and enter server farm configuration mode, use the ip slb serverfarm global configuration command. To remove the server farm from the IOS SLB configuration, use the no form of this command.
ip slb serverfarm serverfarm-name
Syntax Description
serverfarm-name Character string used to identify the server farm. The character string is limited to 15 characters.
Defaults
No default behavior or values.
Command Modes
Global configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example identifies a server farm named PUBLIC and changes the CLI to SLB server farm configuration mode:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)#?
Related Commands
Identifies a real server. Displays information about the server farm configuration.
Command
Description
To identify a virtual server and enter virtual server configuration mode, use the ip slb vserver global configuration command. To remove a virtual server from the IOS SLB configuration, use the no form of this command.
ip slb vserver virtserver-name
Syntax Description
virtserver-name Character string used to identify the virtual server. The character string is limited to 15 characters.
Defaults
No default behavior or values.
Command Modes
Global configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example identifies a virtual server named PUBLIC_HTTP and changes the CLI to SLB virtual server configuration mode:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)#
Related Commands
Associates a real server farm with a virtual server. Displays information about the virtual servers.
Command
Description
To limit the number of active connections to the real server, use the maxconns real server configuration command. To restore the default, use the no form of this command.
maxconns maximum-number
Syntax Description
maximum-number Maximum number of simultaneous active connections on the real server. Valid values range from 1 to 4294967295.
Defaults
Maximum_number default: 4294967295
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example limits the real server to a maximum of 1000 simultaneous active connections:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 SLB-Switch(config-slb-real)# maxconns 1000
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
To configure SLB NAT you must specify which NAT mode is to be using the nat configuration command. To remove a NAT configuration, use the no form of this command.
nat {server | client pool-name}
Syntax Description
server Configures the destination address in load-balanced packets sent to the real server as the address of the real server chosen by the server farm load balancing algorithm. client Configures the client address in load-balanced packets using addresses from the client address pool. pool-name Configures the pool name and must match the pool-name parameter from a previous ip slb probe command.
Defaults
None
Command Modes
Server farm configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
The no nat command is allowed only if the virtual server has been taken out of service by the no inservice command.
Examples
The following example changes to SLB server farm configuration mode and configures NAT mode as server address translation on server farm FARM2:
SLB-Switch# ip slb serverfarm FARM2 SLB-Switch(config-slb-sfarm)# nat server
The following example configures the NAT mode on server farm FARM2 to client translation mode and using the real command configures the real server IP address as 10.3.1.1:
SLB-Switch(config-slb-sfarm)# nat client web-clients
SLB-Switch(config-slb-sfarm)# real 10.3.1.1
Related Commands
Associates a real server farm with a virtual server. Identifies a real server as a member of a server farm. Displays information about the server farm configuration.
Command
Description
To specify the load balancing algorithm for selecting a real server in the server farm, use the predictor server farm configuration command. To restore the default load balancing algorithm of weighted round-robin, use the no form of this command.
predictor [roundrobin | leastconns]
Syntax Description
roundrobin (Optional) Use the weighted round-robin algorithm for selecting the real server to handle the next new connection for the server farm. See the "Weighted Round-Robin" section for a detailed description of this algorithm. leastconns (Optional) Use the weighted least connections algorithm for selecting the real server to handle the next new connection for this server farm. See the "Weighted Least-Connections" section for a detailed description of this algorithm.
Defaults
Weighted round-robin
Command Modes
Server farm configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example specifies the weighted least connections algorithm:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# predictor leastconns
Related Commands
Specifies the real server's capacity, relative to other real servers in the server farm. Displays information about the server farm configuration.
Command
Description
To configure an HTTP probe on a server farm, use the probe configuration command. To remove an HTTP probe configuration, use the no form of this command.
probe probe-name
Syntax Description
probe-name Configures the HTTP probe name and must match the probe-name parameter from a previous ip slb probe command.
Defaults
No default behavior or values.
Command Modes
Server farm configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example configures an HTTP probe named DOGULA on the server farm PUBLIC:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# probe DOGULA SLB-Switch(config-slb-sfarm)# end
Related Commands
Configures the HTTP probe. show running-config Displays the server farm HTTP probe configuration.
Command
Description
To identify a real server as a member of a server farm, use the real server farm configuration command. To remove the real server from the IOS SLB configuration, use the no form of this command.
real ip-address [port_number]
Syntax Description
ip-address Real server IP address. port_number Port translation for the server. Valid values range from 1 to 65535.
Defaults
No default behavior or values.
Command Modes
Server farm configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example identifies a real server as a member of the server farm:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.1.1.1 SLB-Switch(config-slb-real)#
Related Commands
Enables the real server for use by IOS SLB. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
Use the reassign real server configuration command to specify the threshold of consecutive unanswered synchronizations that, if exceeded, result in an attempted connection to a different real server. To restore the default reassignment threshold, use the no form of this command.
reassign threshold
Syntax Description
threshold Number of unanswered TCP synchronizations that are directed to a real server before the connection is reassigned to a different real server. Valid threshold values range from 1 to 4 synchronizations.
Defaults
Threshold default: 3 synchronizations
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example sets the threshold of unanswered synchronizations to 2:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 SLB-Switch(config-slb-real)# reassign 2
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
To configure a stateful backup of SLB decision tables to a backup switch, use the replicate casa virtual server configuration command. To remove a replicate casa configuration, use the no form of this command.
replicate casa listening-ip remote-ip port-number [interval] [password password timeout]
Syntax Description
listening-ip Specifies the listening IP address for state exchange messages that are advertised. remote-ip Specifies the destination IP address for all state exchange signals. port-number The ports and the valid name or number for the port-number argument are as follows: interval (Optional) Maximum replication delivery interval from 1 to 300 seconds. password (Optional) Specifies a password for MD5 authentication. password (Optional) Password value for MD5 authentication. This password must match the password configured on the host agent. timeout (Optional) Delay period, in seconds, during which both the old password and the new password are accepted.
Defaults
interval default: 10 seconds
password timeout default: 180 seconds
Command Modes
Virtual server configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example configures a stateful backup switch with a listening IP address of 10.10.10.11, a remote IP address of 10.10.11.12, over HTTP port 80:
SLB-Switch(config)# ip slb vserver VS1
SLB-Switch(config-slb-vserver)# replicate casa 10.10.10.11 10.10.11.12 4231
Related Commands
Displays the configuration of IP SLB replication. Displays information about the virtual servers.
Command
Description
To configure an HTTP probe to check the status of the real servers, use the request method configuration command. To remove a request method configuration, use the no form of this command.
request method {get | post | head | name name [url path]}
Syntax Description
method Configures the way the data is requested from the server. get Configures the Get method to request data from the server. post Configures the Post method to request data from the server. head Configures the header data type to request data from the server. name Name keyword to be followed by the name of the data to request data from the server. name Configures the name string of the data to send to the servers. The character string is limited to 15 characters. url URL keyword configures the path from the server. path Configures the path from the server.
Defaults
If no values are configured following the method keyword, the default is Get.
If no URL path is set to the server, the default is /.
Command Modes
HTTP SLB probe configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
The request method command configures the HTTP SLB probe method used to receive data from the server. Only one HTTP SLB probe can be configured for each server farm.
Examples
The following example configures an HTTP SLB probe named DOGULA. Changing the CLI to SLB probe submode configures HTTP requests to use the post method and the URL /probe.cgi?all:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# request method post url /probe.cgi?all
Related Commands
Configures the IP SLB probe name. Displays an SLB HTTP probe configuration.
Command
Description
To configure an HTTP probe to check the status of the real servers, use the request configuration command. To remove a request configuration, use the no form of this command.
request [url path]
Syntax Description
url URL keyword configures the path from the server. path Configures the path from the server.
Defaults
If no URL path is set to the server the default is /.
Command Modes
HTTP configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Usage Guidelines
The request method command configures the HTTP SLB probe URL used to receive data from the server. Only one HTTP SLB probe can be configured for each server farm.
Examples
The following example configures an HTTP SLB probe named DOGULA. Changing the CLI to SLB probe submode configures HTTP requests to the URL /probe.cgi?all:
SLB-Switch(config)# ip slb probe DOGULA http
SLB-Switch(config-slb-probe)# request url /probe.cgi?all
Related Commands
Configures the IP SLB probe name. Displays an SLB HTTP probe configuration.
Command
Description
To specify the amount of time that must elapse before a new connection is attempted to a failed server, use the retry real server configuration command. To restore the default retry value, use the no form of this command.
retry retry-value
Syntax Description
retry-value Interval of time, in seconds, that must elapse after the detection of a server failure before a new connection to the server is attempted. Valid values range from 1 to 3600.
Defaults
Retry-value default: 60 seconds
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example specifies that 120 seconds must elapse after the detection of a server failure before a new connection is attempted:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 SLB-Switch(config-slb-real)# retry 120
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
To associate a real server farm with a virtual server, use the serverfarm virtual server configuration command. To remove the server farm association from the virtual server configuration, use the no form of this command.
serverfarm serverfarm-name
Syntax Description
serverfarm-name Name of a server farm that has already been defined using the ip slb serverfarm command.
Defaults
No default behavior or values.
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows how the ip slb vserver, virtual, and serverfarm commands are used to associate the real server farm named PUBLIC with the virtual server named PUBLIC_HTTP.
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# virtual 10.0.0.1 tcp www SLB-Switch(config-slb-vserver)# serverfarm PUBLIC
Related Commands
Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To display the active IOS SLB connections, use the show ip slb conns privileged EXEC command.
show ip slb conns [vserver virtserver-name] [client ip-address] [detail]
Syntax Description
vserver (Optional) Displays only those connections associated with a particular virtual server. virtserver-name (Optional) Name of the virtual server to be monitored. client (Optional) Displays only those connections associated with a particular client IP address. ip-address (Optional) IP address of the client to be monitored. detail (Optional) Displays detailed connection information.
Defaults
If no options are specified, the command displays output for all active IOS SLB connections.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB active connection data:
SLB-Switch# show ip slb conns vserver prot client real state ----------------------------------------------------------------------------- TEST TCP 7.150.72.183:328 80.80.90.25:80 CLOSING TEST TCP 7.250.167.226:423 80.80.90.26:80 CLOSING TEST TCP 7.234.60.239:317 80.80.90.26:80 CLOSING TEST TCP 7.110.233.96:747 80.80.90.26:80 CLOSING TEST TCP 7.162.0.201:770 80.80.90.30:80 CLOSING TEST TCP 7.22.225.219:995 80.80.90.26:80 CLOSING TEST TCP 7.2.170.148:169 80.80.90.30:80 CLOSING
| Field | Description |
vserver | Name of the virtual server whose connections are being monitored and displayed. Information about each connection is displayed on a separate line. |
prot | Protocol being used by the connection. |
client | Client IP address being used by the connection. |
real | Real IP address of the connection. |
state | Current state of the real server:
|
To display DFP manager and agent information, such as passwords, timeouts, retry counts, and weights, use the show ip slb dfp privileged EXEC command.
show ip slb dfp [agent ip_address port | detail | weights]
Syntax Description
agent (Optional) Displays information about an agent. ip_address (Optional) Agent IP address. port (Optional) Agent port number. detail (Optional) Displays all data available. weights (Optional) Displays information about weights assigned to real servers for load balancing.
Defaults
If no options are specified, the command displays summary information.
Command Modes
Privileged EXEC
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB DFP data:
SLB-Switch# show ip slb dfp detail
DFP Manager:
Current passwd:NONE Pending passwd:NONE
Passwd timeout:0 sec
Unexpected errors:0
DFP Agent 161.44.2.34:61936 Connection state:Connected
Timeout = 0 Retry Count = 0 Interval = 180 (Default)
Security errors = 0
Last message received:10:20:26 UTC 11/02/99
Last reported Real weights for Protocol TCP, Port www
Host 17.17.17.17 1 Weight 1
Host 68.68.68.68 Bind ID 4 Weight 4
Host 85.85.85.85 Bind ID 5 Weight 5
Last reported Real weights for Protocol TCP, Port 22
Host 17.17.17.17 Bind ID 111 Weight 111
SLB-Switch# show ip slb dfp weights
Real IP Address 17.17.17.17 Protocol TCP Port 22 Bind_ID 111 Weight 111
Set by Agent 161.44.2.3458490 at 132241 UTC 12/03/99
Real IP Address 17.17.17.17 Protocol TCP Port www Bind_ID 1 Weight 1
Set by Agent 161.44.2.3458490 at 132241 UTC 12/03/99
Real IP Address 68.68.68.68 Protocol TCP Port www Bind_ID 4 Weight 4
Set by Agent 161.44.2.3458490 at 132241 UTC 12/03/99
Real IP Address 85.85.85.85 Protocol TCP Port www Bind_ID 5 Weight 5
Set by Agent 161.44.2.3458490 at 132241 UTC 12/03/99
SLB-Switch# show ip slb dfp
DFP Manager:
Current passwd:NONE Pending passwd:NONE
Passwd timeout:0 sec
Agent IP Port Timeout Retry Count Interval
--------------------------------------------------------
161.44.2.34 61936 0 0 180 (Default)
| Field | Description |
Agent IP | IP address of the agent about which information is being displayed. |
Port | Port number of the agent. |
Timeout | Time period, in seconds, during which the DFP manager must receive an update from the DFP agent. A value of 0 means there is no timeout. |
Retry Count | Number of times the DFP manager attempts to establish the TCP connection to the DFP agent. A value of 0 means there are infinite retries. |
Interval | Interval, in seconds, between retries. |
State |
|
To display the IP SLB NAT configuration, use the show ip slb natpool command.
show ip slb natpool [name pool-name] [detail]
Syntax Description
name Keyword to display a specific NAT pool. pool-name NAT pool name string to display. detail Lists all the interval ranges currently allocated in the client NAT pool.
Defaults
No default behavior or values.
Command Modes
EXEC configuration
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example displays the default show ip slb natpool command:
SLB-Switch# show ip slb natpool nat client B 1.1.1.6 1.1.1.8 Netmask 255.255.255.0 nat client A 1.1.1.1 1.1.1.5 Netmask 255.255.255.0
The following example displays the show ip slb natpool command with the additional detail parameter:
SLB-Switch# show ip slb natpool detail
nat client A 1.1.1.1 1.1.1.5 Netmask 255.255.255.0
Start NAT Last NAT Count ALLOC/FREE
-------------------------------------------------------
1.1.1.1:11001 1.1.1.1:16333 0005333 ALLOC
1.1.1.1:16334 1.1.1.1:19000 0002667 ALLOC
1.1.1.1:19001 1.1.1.5:65535 0264675 FREE
nat client B 1.1.1.6 1.1.1.8 Netmask 255.255.255.0
Start NAT Last NAT Count ALLOC/FREE
-------------------------------------------------------
1.1.1.6:11001 1.1.1.6:16333 0005333 ALLOC
1.1.1.6:16334 1.1.1.6:19000 0002667 ALLOC
1.1.1.6:19001 1.1.1.8:65535 0155605 FREE
Related Commands
Configures the SLB NAT.
Command
Description
To display an SLB HTTP probe, use the show ip slb probe configuration command.
show ip slb probe [name probe_name] [detail]
Syntax Description
name (Optional) Displays information about the specific probe named. probe_name (Optional) Probe name to display. detail (Optional) Displays detailed information.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB HTTP probe data:
SLB-Switch# show ip slb probe detail Server:Port Status Outages Current Cumulative ---------------------------------------------------------- 10.11.2.2:80 200 0 never 00:00:00
| Field | Description |
Server:Port | IP address and port of the of the real server. |
Status | If the status is "0" the probe has not failed. A number greater than 0 indicates the number of times the probe has failed. |
Outage | Interval between successful probes. |
Current | Time since the last probe failure. |
Cumulative | Total time the real server has been under test by the probe and has failed the probe test. |
To display information about the real servers, use the show ip slb reals privileged EXEC command.
show ip slb reals [vserver virtserver-name] [detail]
Syntax Description
vserver (Optional) Displays information about only those real servers associated with a particular virtual server. virtserver-name (Optional) Name of the virtual server. detail (Optional) Displays detailed information.
Defaults
If no options are specified, the command displays information about all real servers.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB real server data:
SLB-Switch# show ip slb reals real server farm weight state conns ---------------------------------------------------------------- 80.80.2.112 FRAG 8 OUTOFSERVICE 0 80.80.5.232 FRAG 8 INSERVICE 0 80.80.15.124 FRAG 8 OUTOFSERVICE 0 80.254.2.2 FRAG 8 OUTOFSERVICE 0 80.80.15.124 LINUX 8 INSERVICE 0 80.80.15.125 LINUX 8 INSERVICE 0 80.80.15.126 LINUX 8 INSERVICE 0 80.80.90.25 SRE 8 INSERVICE 220 80.80.90.26 SRE 8 INSERVICE 216 80.80.90.27 SRE 8 INSERVICE 216 80.80.90.28 SRE 8 TESTING 1 80.80.90.29 SRE 8 INSERVICE 221 80.80.90.30 SRE 8 INSERVICE 224 80.80.30.3 TEST 100 READY_TO_TEST 0 80.80.30.4 TEST 100 READY_TO_TEST 0 80.80.30.5 TEST 100 READY_TO_TEST 0 80.80.30.6 TEST 100 READY_TO_TEST 0
| Field | Description |
real | Information about each real server is displayed on a separate line. |
server farm | Name of the server farm associated to the real server. |
weight | Weight assigned to the real server. The weight identifies the real server's capacity, relative to other real servers in the server farm. |
state | Current state of the real server.
|
To display the SLB replication configuration, use the show ip slb replicate privileged EXEC command.
show ip slb replicateDefaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.0(10)W5(18) This command was introduced.
Release
Modification
Examples
The following example displays the SLB replication configuration:
SLB-Switch# show ip slb replicate
VS1, local = 10.10.99.132 remote = 10.10.99.99 port = 1024
current password = none pending password = none
password timeout = 180 sec (Default)
unsent conn updates: 0
conn updates received: 32
conn updates transmitted: 471
update packets received: 12
update packets transmitted: 34
failovers: 0
SLB-Switch#
Related Commands
Configures SLB replication.
Command
Description
To display information about the server farms, use the show ip slb serverfarms privileged EXEC command.
show ip slb serverfarms [name serverfarm-name] [detail]
Syntax Description
name (Optional) Displays information about only a particular server farm. serverfarm-name (Optional) Name of the server farm. detail (Optional) Displays detailed server farm information.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB server farm data:
SLB-Switch# show ip slb serverfarms server farm predictor reals bind id ------------------------------------------------- FRAG ROUNDROBIN 4 0 LINUX ROUNDROBIN 3 0 SRE ROUNDROBIN 6 0 TEST ROUNDROBIN 4 0
| Field | Description |
server farm | Name of the server farm about which information is being displayed. Information about each server farm is displayed on a separate line. |
predictor | Type of load balancing algorithm (ROUNDROBIN or LEASTCONNS) used by the server farm. |
reals | Number of real servers configured in the server farm. |
bind id | Bind ID configured on the server farm. |
To display SLB statistics, use the show ip slb stats privileged EXEC command.
show ip slb statsSyntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows IOS SLB statistics:
SLB-Switch# show ip slb stats Pkts via normal switching: 530616 Pkts via special switching:1812710 Connections Created: 783774 Connections Established: 633418 Connections Destroyed: 782752 Connections Reassigned: 0 Zombie Count: 0
| Field | Description |
Pkts via normal switching | Number of packets that have been handled by IOS SLB via normal switching since the last time counters were cleared. |
Pkts via special switching | Number of packets that have been handled by IOS SLB via special switching since the last time counters were cleared. |
Connections Created | Number of connections that have been created since the last time counters were cleared. |
Connections Established | Number of connections that have been created and have become established since the last time counters were cleared. |
Connections Destroyed | Number of connections that have been destroyed since the last time counters were cleared. |
Connections Reassigned | Number of connections that have been reassigned to a different real server since the last time counters were cleared. |
Zombie Count | Number of connections that are currently pending destruction, awaiting a timeout or some other condition to be met. |
To display the IOS SLB sticky database, use the show ip slb sticky privileged EXEC command.
show ip slb sticky [client ip_address]
Syntax Description
client (Optional) Displays only those sticky database entries associated with a particular client IP address. ip-address (Optional) IP address of the client.
Defaults
If no options are specified, the command displays information about all virtual servers.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows the IOS SLB sticky database:
SLB-Switch# show ip slb sticky client netmask group real conns ----------------------------------------------------------------------- 10.10.2.12 255.255.0.0 4097 10.10.3.2 1 SLB-Switch#
| Field | Description |
client | Client IP address which is bound to this sticky assignment. |
netmask | Subnet mask for this sticky assignment. |
group | Group ID for this sticky assignment. |
real | Real server used by all clients connecting with the client IP address detailed on this line. |
conns | Number of connections currently sharing this sticky assignment. |
To display information about the virtual servers, use the show ip slb vservers privileged EXEC command.
show ip slb vservers [name virtserver-name] [detail]
Syntax Description
name (Optional) Only displays information about a particular server farm. serverfarm-name (Optional) Name of the server farm. detail (Optional) Displays detailed server farm information.
Defaults
If no options are specified, the command displays information about all virtual servers.
Command Modes
Privileged EXEC
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example shows virtual server data:
SLB-Switch# show ip slb vservers slb vserver prot virtual state conns ------------------------------------------------------------------ TEST TCP 80.80.254.3:80 INSERVICE 1013 TEST21 TCP 80.80.254.3:21 OUTOFSERVICE 0 TEST23 TCP 80.80.254.3:23 OUTOFSERVICE 0
| Field | Description |
slb vserver | Name of the virtual server about which information is being displayed. Information about each virtual server is displayed on a separate line. |
prot | Protocol being used by the virtual server detailed on a given line. |
virtual | Virtual IP address of the virtual server detailed on a given line. |
state | Current state of the virtual server detailed on a given line. |
conns | Number of connections associated with the virtual server detailed on a given line. |
To assign all connections from a client to the same real server, use the sticky virtual server configuration command. To remove the client/server coupling use the no form of this command.
sticky duration [group group-id] [netmask netmask]
Syntax Description
duration Sticky timer duration in seconds. Valid values range from 0 to 65535. group (Optional) Keywork places the virtual server in a sticky group, for coupling of services. group-id (Optional) Number identifying the sticky group to which the virtual server belongs. Valid values range from 0 to 255. netmask (Optional) Keyword places the virtual server as part of a sticky subnetwork, for coupling of services. netmask (Optional) Sticky subnet mask number.
Defaults
Sticky connections are not tracked.
Virtual servers are not associated with any groups.
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
The last real server that was used for a connection from a client is stored for the set duration seconds. If a new connection from the client to the virtual server is initiated during that time, the same real server that was used for the previous connection is chosen for the new connection. If two virtual servers are placed in the same group, coincident connection requests for those services from the same IP address are handled by the same real server.
Examples
The following example specifies that if a client's subsequent request for a virtual server is made within 60 seconds of the previous request, then the same real server is used for the connection. This example also places the virtual server in group 10.
SLB-Switch(config)# ip slb vserver VS1 SLB-Switch(config-slb-vserver)# sticky 60 group 10
Related Commands
Displays information about the virtual server sticky configuration. Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To limit the rate of TCP synchronizations handled by a virtual server to prevent a synchronization flood denial of service attack, use the synguard virtual server configuration command. To remove the threshold, use the no form of this command.
synguard syn-count [interval]
Syntax Description
syn-count Number of unanswered synchronizations that are allowed to be outstanding to a virtual server. Valid values range from 0 (off) to 4294967295. interval (Optional) Interval, in milliseconds, for synchronization threshold monitoring. Valid values range from 50 to 5000.
Defaults
Syn-count default: 0 (off)
Interval default: 100 ms
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example sets the threshold of unanswered synchronizations to 50:
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# synguard 50
Related Commands
Configures the virtual server attributes. Displays information about the virtual servers.
Command
Description
To configure virtual server attributes, use the virtual server configuration command. To remove the attributes, use the no form of this command.
virtual ip-address {tcp | udp} port-number [service service-name]
Syntax Description
ip-address IP address for this virtual server instance, used by clients to connect to the server farm. tcp Perform load balancing for only TCP connections. udp Perform load balancing for only UDP connections. port-number IOS SLB virtual port (the TCP or UDP port number or port name). If specified, only the connections for the specified port on the server are load balanced. The ports and the valid name or number for the port-number argument are as follows: service (Optional) Couple connections associated with a given service, such as HTTP or Telnet, so all related connections from the same client use the same real server. service-name (Optional) Type of connection coupling. Currently, the only choice is:
Defaults
No default behavior or values
Command Modes
Virtual server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Usage Guidelines
The no virtual command is allowed only if the virtual server has been taken out of service by the no inservice command.
Examples
The following example specifies that the virtual server with the IP address 10.0.0.1 performs load balancing for TCP connections for the port named www. The virtual server processes HTTP requests.
SLB-Switch(config)# ip slb vserver PUBLIC_HTTP SLB-Switch(config-slb-vserver)# virtual 10.0.0.1 tcp www
Related Commands
Identifies a virtual server. Displays information about the virtual servers.
Command
Description
To specify a real server's capacity, relative to other real servers in the server farm, use the weight real server configuration command. To restore the default weight value, use the no form of this command.
weight weighting-value
Syntax Description
weighting-value Weighting value to use for real server predictor algorithm. Valid values range from 1 to 255.
Defaults
Weighting-value default: 8
Command Modes
Real server configuration
Command History
12.0(7)XE This command was introduced.
Release
Modification
Examples
The following example specifies the relative weighting values of three real servers as 16, 8 (by default), and 24, respectively:
SLB-Switch(config)# ip slb serverfarm PUBLIC SLB-Switch(config-slb-sfarm)# real 10.10.1.1 First real server SLB-Switch(config-slb-real)# weight 16 Assigned weight of 16 SLB-Switch(config-slb-real)# inservice Enabled SLB-Switch(config-slb-real)# exit SLB-Switch(config-slb-sfarm)# real 10.10.1.2 Second real server SLB-Switch(config-slb-real)# inservice Enabled; default weight SLB-Switch(config-slb-real)# exit SLB-Switch(config-slb-sfarm)# real 10.10.1.3 Third real server SLB-Switch(config-slb-real)# weight 24 Assigned weight of 24; not enabled
Related Commands
Identifies a real server. Displays information about the server farm configuration. Displays information about the real servers.
Command
Description
For IP, HSRP allows one SLB switch to automatically assume the function of the second SLB switch if it fails.
To configure an authentication string for the Hot Standby Router Protocol (HSRP), use the standby authentication interface configuration command. To delete an authentication string, use the no form of this command.
standby [group-number] authentication string
Syntax Description
group-number (Optional) Group number on the interface to which this authentication string applies. string Authentication string. It can be up to eight characters in length.
Defaults
group-number: 0
string: cisco
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The authentication string is transmitted unencrypted in all HSRP messages. The same authentication string must be configured on all routers and access servers on a cable to ensure interoperation. Authentication mismatch prevents a device from learning the designated Hot Standby IP address and the Hot Standby timer values from other routers configured with HSRP. Authentication mismatch does not prevent protocol events such as one router taking over as the designated router.
When group number 0 is used, no group number is written to NVRAM, providing backward compatibility.
Examples
In the following example, "word" is configured as the authentication string required to allow Hot Standby routers in group 1 to interoperate:
SLB-Switch(config)# interface fastethernet 1
SLB-Switch(config-if)# standby 1 authentication word
To configure Hot Standby Router Protocol (HSRP) priority, preemption, and preemption delay, use the standby interface configuration command. To restore the default values, use the no form of this command.
standby [group-number] priority priority [preempt [delay delay]]
Syntax Description
group-number (Optional) Group number on the interface to which the other arguments in this command apply. priority priority (Optional) Priority value that prioritizes a potential Hot Standby router. The range is 1 to 255. preempt delay delay (Optional) Time in seconds. The delay argument causes the local router to postpone taking over the active role for delay seconds since that router was last restarted. The range is 0 to 3600 seconds (1 hour).
Defaults
group-number: 0
priority: 100
delay: 0 seconds; if the router wants to preempt, it will do so immediately.
Command Modes
Interface configuration
Command History
11.3 This command was introduced.
Release
Modification
Usage Guidelines
When using this command, you must specify at least one keyword (priority or preempt), or you can specify both.
When group number 0 is used, no group number is written to NVRAM, providing backward compatibility.
The assigned priority is used to help select the active and standby routers. Assuming preemption is enabled, the router with the highest priority becomes the designated active router. In case of ties, the primary IP addresses are compared, and the higher IP address has priority.
Note that the device's priority can change dynamically if an interface is configured with the standby track command and another interface on the router goes down.
When a router first comes up, it does not have a complete routing table. If it is configured to preempt, it will become the active router, yet it is unable to provide adequate routing services. This problem is solved by configuring a delay before the preempting router actually preempts the currently active router.
Examples
In the following example, the router has a priority of 120 (higher than the default value) and will wait for 300 seconds (5 minutes) before attempting to become the active router:
SLB-Switch(config)# interface fastethernet 1
SLB-Switch(config-if)# standby ip 172.19.108.254
SLB-Switch(config-if)# standby priority 120 preempt delay 300
Related Commands
Configures the standby track on an interface so that the Hot Standby priority changes based on the availability of other interfaces.
Command
Description
To configure the time between hellos and the time before other routers declare the active Hot Standby or standby router to be down, use the standby timers interface configuration command. To restore the timers to their default values, use the no form of this command.
standby [group-number] timers hellotime holdtime
Syntax Description
group-number (Optional) Group number on the interface to which the timers apply. hellotime Hello interval in seconds. This is an integer from 1 to 255. holdtime Time in seconds before the active or standby router is declared to be down. This is an integer from 1 to 255.
Defaults
group-number: 0
hellotime: 3 seconds
holdtime: 3 seconds
Command Modes
Interface configuration
Command History
10.0 This command was introduced.
Release
Modification
Usage Guidelines
The standby timers command configures the time between standby hellos and the time before other routers declare the active or standby router to be down. Routers or access servers on which timer values are not configured can learn timer values from the active or standby router. The timers configured on the active router always override any other timer settings. All routers in a Hot Standby group should use the same timer values. Normally, holdtime is greater than or equal to 3 times hellotime (holdtime > 3 * hellotime).
When group number 0 is used, no group number is written to NVRAM, providing backward compatibility.
Examples
In the following example, for group number 1 on Fast Ethernet interface 1, the time between hello packets is set to 5 seconds, and the time after which a router is considered to be down is set to 15 seconds:
SLB-Switch(config)# interface fastethernet 1
SLB-Switch(config-if)# standby 1 ip
SLB-Switch(config-if)# standby 1 timers 5 15
To configure an interface so that the Hot Standby priority changes based on the availability of other interfaces, use the standby track interface configuration command. To remove the tracking, use the no form of this command.
standby [group-number] track type number [interface-priority]
Syntax Description
group-number (Optional) Group number on the interface to which the tracking applies. type Interface type (combined with interface number) that will be tracked. number Interface number (combined with interface type) that will be tracked. interface-priority (Optional) Amount by which the Hot Standby priority for the router is decremented (or incremented) when the interface goes down (or comes back up).
Defaults
group-number: 0
interface-priority: 10
Command Modes
Interface configuration
Command History
10.3 This command was introduced.
Release
Modification
Usage Guidelines
This command ties the router's Hot Standby priority to the availability of its interfaces. It is useful for tracking interfaces that are not configured for the Hot Standby Router Protocol.
When a tracked interface goes down, the Hot Standby priority decreases by 10. If an interface is not tracked, its state changes do not affect the Hot Standby priority. For each interface configured for Hot Standby, you can configure a separate list of interfaces to be tracked.
The optional argument interface-priority specifies how much to decrement the Hot Standby priority by when a tracked interface goes down. When the tracked interface comes back up, the priority is incremented by the same amount.
When multiple tracked interfaces are down and interface-priority values have been configured, these configured priority decrements are cumulative. If tracked interfaces are down, but none of them were configured with priority decrements, the default decrement is 10 and it is noncumulative.
When group number 0 is used, no group number is written to NVRAM, providing backward compatibility.
Examples
In the following example, Fast Ethernet interface 1 tracks Fast Ethernet interface 10 and Gigabit Ethernet interface 49. If one or both of these two interfaces go down, the Hot Standby priority of the router decreases by 10. Because the default Hot Standby priority is 100, the priority becomes 90 when one or both of the tracked interfaces go down.
SLB-Switch(config)# interface fastethernet 1 SLB-Switch(config-if)# ip address 198.92.72.37 255.255.255.240 SLB-Switch(config-if)# no ip redirects SLB-Switch(config-if)# standby track fastethernet 10 SLB-Switch(config-if)# standby track gigabitethernet 49 SLB-Switch(config-if)# standby preempt SLB-Switch(config-if)# standby ip 198.92.72.46
Related Commands
Configures the Hot Standby Router Protocol (HSRP) priority, preemption, and preemption delay.
Command
Description
Posted: Thu Sep 28 15:30:10 PDT 2000
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