Specifications

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 7 Clustering Switches
Planning a Switch Cluster
If the active command switch fails, the standby command switch assumes ownership of the virtual IP
address and becomes the active command switch. The passive switches in the cluster standby group
compare their assigned priorities to determine the new standby command switch. The passive standby
switch with the highest priority then becomes the standby command switch. When the previously active
command switch becomes active again, it resumes its role as the active command switch, and the current
active command switch becomes the standby command switch again. For more information about IP
address in switch clusters, see the “IP Addresses” section on page 7-16.
Other Considerations for Cluster Standby Groups
These requirements also apply:
• Standby command switches must meet these requirements:
– When the command switch is a Catalyst 3550 switch, all standby command switches must be
Catalyst 3550 switches.
– When the command switch is a Catalyst 2955 switch running Release 12.1(12c)EA1 or later, all
standby command switches must be Catalyst 2955 switches running Release 12.1(12c)EA1 or
later.
– When the command switch is a Catalyst 2950 switch running Release 12.1(9)EA1 or later, all
standby command switches must be Catalyst 2950 switches running Release 12.1(9)EA1 or
later.
– When the command switch is a Catalyst 2950 switch running Release 12.1(6)EA2 or later, all
standby command switches must be Catalyst 2950 switches running Release 12.1(6)EA2 or
later.
– When the command switch is running Release 12.0(5)WC2 or earlier, the standby command
switches can be these switches: Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL
switches.
We strongly recommend that the command switch and standby command switches are of the same
switch platform.
– If you have a Catalyst 3550 command switch, the standby command switches should be
Catalyst 3550 switches.
– If you have a Catalyst 2955 command switch, the standby command switches should be
Catalyst 2955 switches.
– If you have a Catalyst 2950 command switch, the standby command switches should be
Catalyst 2950 switches.
– If you have a Catalyst 2900 XL or Catalyst 3500 XL command switch, the standby command
switches should be Catalyst 2900 XL and Catalyst 3500 XL switches.
• Only one cluster standby group can be assigned to a cluster.
• All standby-group members must be members of the cluster.
Note There is no limit to the number of switches that you can assign as standby command
switches. However, the total number of switches in the cluster—which would include the
active command switch, standby-group members, and member switches—cannot be more
than 16.