Automatic Recovery Of Cluster Configuration - Cisco Catalyst 3550 series Software Configuration Manual

Chapter 6 Clustering Switches
Figure 6-9
Catalyst 3550
Catalyst 2950

Automatic Recovery of Cluster Configuration

The active command switch continually forwards cluster-configuration information (but not
device-configuration information) to the standby command switch. This ensures that the standby
command switch can take over the cluster immediately after the active command switch fails.
Automatic discovery has these limitations:
•
•
•
When the previously active command switch resumes its active role, it receives a copy of the latest
cluster configuration from the active command switch, including members that were added while it was
down. The active command switch sends a copy of the cluster configuration to the cluster standby group.
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VLAN Connectivity between Standby-Group Members and Cluster Members
Catalyst 3550 active
command switch
VLANs 9,16
Si
VLAN 9
VLAN 9
switch
Management
VLAN 9
switch
This limitation applies only to clusters that have Catalyst 2950, Catalyst 2955, and Catalyst 3550
command and standby command switches: If the active command switch and standby command
switch become disabled at the same time, the passive command switch with the highest priority
becomes the active command switch. However, because it was a passive standby command switch,
the previous command switch did not forward cluster-configuration information to it. The active
command switch only forwards cluster-configuration information to the standby command switch.
You must therefore rebuild the cluster.
This limitation applies to all clusters: If the active command switch fails and there are more than
two switches in the cluster standby group, the new command switch does not discover any
Catalyst 1900, Catalyst 2820, and Catalyst 2916M XL member switches. You must re-add these
member switches to the cluster.
This limitation applies to all clusters: If the active command switch fails and becomes active again,
it does not discover any Catalyst 1900, Catalyst 2820, and Catalyst 2916M XL member switches.
You must again add these member switches to the cluster.
Catalyst 3550 passive
command switch
VLANs 9,16
Si
VLAN 9
Management
VLAN 16
Member switches
Catalyst 3550 Multilayer Switch Software Configuration Guide
Planning a Switch Cluster
Catalyst 3550 standby
command switch
Si
Management
VLAN 16
Catalyst 2900 XL or
Catalyst 3500 XL
switch
VLAN 16
Catalyst 3550
multilayer switch
Si
6-15