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Catalyst 3750 Switch Software Configuration Guide
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Chapter 6 Clustering Switches
Planning a Switch Cluster
• All stack members should have redundant connectivity to all VLANs in the switch cluster.
Otherwise, if a new stack master is elected, stack members connected to any VLANs not configured
on the new stack master lose their connectivity to the switch cluster. You must change the VLAN
configuration of the stack master or the stack members and add the stack members back to the switch
cluster.
• If a cluster member switch stack reloads and a new stack master is elected, the switch stack loses
connectivity with the cluster command switch. You must add the switch stack back to the switch
cluster.
• If a cluster command switch stack reloads, and the original stack master is not re-elected, you must
rebuild the entire switch cluster.
For more information about switch stacks, see Chapter 5, “Managing Switch Stacks,”
TACACS+ and RADIUS
Inconsistent authentication configurations in switch clusters cause CMS to continually prompt for a user
name and password. If Terminal Access Controller Access Control System Plus (TACACS+) is
configured on a cluster member, it must be configured on all cluster members. Similarly, if RADIUS is
configured on a cluster member, it must be configured on all cluster members. Further, the same switch
cluster cannot have some members configured with TACACS+ and other members configured with
RADIUS.
For more information about TACACS+, see the “Controlling Switch Access with TACACS+” section on
page 9-10. For more information about RADIUS, see the “Controlling Switch Access with RADIUS”
section on page 9-18.
Access Modes in CMS
If your cluster has these cluster member switches running earlier software releases and if you have
read-only access to these cluster member switches, some configuration windows for those switches
display incomplete information:
• Catalyst 2900 XL or Catalyst 3500 XL cluster member switches running Cisco IOS
Release 12.0(5)WC2 or earlier
• Catalyst 2950 cluster member switches running Cisco IOS Release 12.0(5)WC2 or earlier
• Catalyst 3550 cluster member switches running Cisco IOS Release 12.1(6)EA1 or earlier
These switches do not support read-only mode on CMS:
• Catalyst 1900 and Catalyst 2820
• Catalyst 2900 XL switches with 4-MB CPU DRAM
In read-only mode, these switches appear as unavailable devices and cannot be configured from CMS.
For more information about CMS access modes, see the “Access to Older Switches in a Cluster” section
on page 3-7.
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