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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter5 Clustering Switches
Planning a Switch Cluster
Considerations for Cluster Standby Groups
In addition to providing a virtual IP address to the cluster stand by gro up, t hese r equi reme nts ap ply:
•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 Ci sco IOS Release 12.0(5)WC2 o r
earlier: Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL switches.
We recommend that the standby command switches be of the sa me platfo rm family as the comm and
switch. For example, a cluster with a Catalyst 3550 command switch should ha ve Ca ta lyst 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 redund ancy becomes disabled on
that group. You can reenable it by using the CLI. For more information about HS RP and ro uter
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 co mmand switches.
However, the total number of switches in the cluster—which would include the active
command switch, standby-group members, and member switches—can not 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 red und an tly conn ec ted to ea ch
other through at least one VLAN in common with the switch cluster.
Catalyst 1900, Catalyst 2820, Catalyst 290 0 XL, Catalyst 2950, and Catalyst 3500 XL member
switches must be connected to the cluster standby group through t hei r ma na geme nt V LANs.
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 page5-8