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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 5 Clustering Switches
Planning a Switch Cluster
Considerations for Cluster Standby Groups
In addition to providing a virtual IP address to the cluster standby group, these requirements apply:
•
When the command switch is a Catalyst 3550 switch, all standby command switches must be
Catalyst 3550 switches or Catalyst 2950 switches running Cisco IOS Release 12.1(6)EA2 or later.
When the command switch is a Catalyst 2950 switch running Cisco IOS Release 12.1(6)EA2 or
later, all standby command switches must be Catalyst 2950 switches running Cisco IOS
Release 12.1(6)EA2 or later.
When the Catalyst 2950 command switch is running Cisco IOS Release 12.0(5)WC2 or earlier, the
standby command switches can be these switches also running Cisco IOS Release 12.0(5)WC2 or
earlier: Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL switches.
We recommend that the standby command switches be of the same platform family as the command
switch. For example, a cluster with a Catalyst 3550 command switch should have Catalyst 3550
standby command switches.
•
Only one cluster standby group can be assigned to a cluster. You can have more than one
router-redundancy standby group.
An HSRP group can be both a cluster standby group and a router-redundancy group. However, if a
router-redundancy group becomes a cluster standby group, router redundancy becomes disabled on
that group. You can reenable it by using the CLI. For more information about HSRP and router
redundancy, see
Chapter 23, “Configuring HSRP.”
•
All standby-group members must be members of the cluster.
Note
There is no limit to the number of switches 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.
•
The active command switch must be connected through the same VLAN to each standby-group
member (
Figure 5-8
). Each standby-group member must also be redundantly connected to each
other through at least one VLAN in common with the switch cluster.
Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL member
switches must be connected to the cluster standby group through their management VLANs.
For more information about VLANs in switch clusters, see these sections:
–
“Discovery through Different VLANs” section on page 5-7
–
“Discovery through Different Management VLANs” section on page 5-9
–
“Discovery through the Same Management VLAN” section on page 5-8
