Chapter 5      Clustering Switches
Using SNMP to Manage Switch Clusters
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Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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Using SNMP to Manage Switch Clusters
You must enable SNMP for the Cluster Management reporting and graphing 
features to function properly. When you first power on the switch, SNMP is 
enabled if you enter the IP information by using the setup program and accept its 
proposed configuration. If you did not use the setup program to enter the IP 
information and SNMP was not enabled, you can enable it on the SNMP 
Configuration page described in the “Configuring SNMP” section on page 6-18. 
On Catalyst 1900 and Catalyst 2820 switches, SNMP is enabled by default.
When you create a cluster, the command switch manages the exchange of 
messages between member switches and an SNMP application. The Cluster 
Management software appends the member switch number (@esN, where N is the 
switch number) to the first configured RW and RO community strings on the 
command switch and propagates them to the member switch. The command 
switch uses this community string to control the forwarding of gets, sets, and 
get-next messages between the SNMP management station and the member 
switches. 
Note When a standby group is configured, the command switch can change without 
your knowledge. Use the first read-write and read-only community strings to 
communicate with the command switch if there is a standby group configured 
for the cluster.
If the member switch does not have an IP address, the command switch passes 
traps from the member switch to the management station, as shown in Figure 5-7. 
If a member switch has its own IP address and community strings, they can be 
used in addition to the access provided by the command switch. For more 
information, see the “SNMP Community Strings” section on page 5-10 and the 
“Configuring SNMP” section on page 6-18.