Cluster Management software implements the Hot Standby Router Protocol (HSRP), which transfers responsibilities to another switch if the command switch becomes unavailable. The HSRP group is composed of cluster members that are designated to take command if needed. The transfer of responsibilities to a standby switch (failover) is transparent.
With the Standby Command Configuration window, you can:
Note: Failovers normally require 13 to 17 seconds to reestablish connections to member switches, but this process can require as long as 2 minutes depending on the availability of member information being transferred.
The Candidates list contains the name of all cluster members that are qualified standby switches: command-capable switches with the required software that are available to assume responsibility. On this list, switches are listed in order of eligibility to serve as the cluster command switch. A candidate's eligibility is determined primarily by the number of links that it has to other cluster switches and its speed (see the Cisco IOS Desktop Switching Software Configuration Guide for details).
If HSRP is not configured on the cluster, the Selected list contains only the name of the command switch with the CC (cluster command) designation. If HSRP is configured, this list contains the names of the active command (AC) switch, the standby command (SC) switch, and one or more passive standby (PC) switches. A passive standby replaces the switch listed above it if the current standby (SC) becomes the active command switch.
Switches listed in the Selected list make up the current cluster HSRP group. These switches share a virtual IP address, which is assigned to the cluster. Because a network can contain several HSRP groups, each HSRP group is identified by a number.
Note: After a virtual IP is assigned to the cluster HSRP group, always use the virtual IP address to access the command switch.
To create an HSRP group and enable the standby:
You can add any switch in the Candidates list to the Selected list to add it to the cluster HSRP group. You can remove any switch from the Selected list except the active command (AC) switch.
Note: If you remove all standby switches from the Selected list, the cluster HSRP group is removed.
To add a switch to the HSRP group:
To remove a switch from the HSRP group:
To remove an HSRP group, click Remove Standby Configuration. Then, click OK to put your changes in effect and close the Standby Command Configuration window.