Cisco Systems NME-16ES-1G manual Automatic Recovery of Cluster Configuration

Cisco EtherSwitch Service Modules Feature Guide

Information About the Cisco EtherSwitch Service Modules

•Each standby-group member (Figure 7) must be connected to the cluster command switch through the same VLAN. In this example, the cluster command switch and standby cluster command switches are Cisco EtherSwitch service module cluster command switches. Each standby-group member must also be redundantly connected to each other through at least one VLAN in common with the switch cluster.

For more information about VLANs in switch clusters, see these sections:

–“Discovery of Candidates and Members Through Different VLANs” section on page 24

–“Discovery of Candidates and Members Through Different Management VLANs” section on page 24

Figure 7			VLAN Connectivity Between Standby-Group Members and Cluster Members
	Command			Passive		Standby
		device		command device	command device
			VLANs 9,16	VLANs 9,16
							Management
VLAN 9							VLAN 16

Management VLAN 9

VLAN 9	Management
	VLAN 16

Member devices

VLAN 16

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Automatic Recovery of Cluster Configuration

The active cluster command switch continually forwards cluster configuration information (but not device configuration information) to the standby cluster command switch. This ensures that the standby cluster command switch can take over the cluster immediately after the active cluster command switch fails.

Automatic discovery has these limitations:

•This limitation applies only to clusters that have Cisco EtherSwitch service module command and standby cluster command switches: If the active cluster command switch and standby cluster command switch become disabled at the same time, the passive cluster command switch with the highest priority becomes the active cluster command switch. However, because it was a passive standby cluster command switch, the previous cluster command switch did not forward cluster configuration information to it. The active cluster command switch only forwards cluster configuration information to the standby cluster command switch. You must therefore rebuild the cluster.

•This limitation applies to all clusters: If the active cluster command switch fails and there are more than two switches in the cluster standby group, the new cluster command switch does not discover any Catalyst 1900, Catalyst 2820, and Catalyst 2916M XL cluster member switches. You must again add these cluster member switches to the cluster.

Cisco IOS Release 12.2(25)SEC

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