Cisco Systems 3750E manual Switch Cisco IOS Release Cluster Capability

Chapter 6 Clustering Switches

Understanding Switch Clusters

In a switch cluster, 1 switch must be the cluster command switch and up to 15 other switches can be cluster member switches. The total number of switches in a cluster cannot exceed 16 switches. The cluster command switch is the single point of access used to configure, manage, and monitor the cluster member switches. Cluster members can belong to only one cluster at a time.

Note A switch cluster is different from a switch stack. A switch stack is a set of Catalyst 3750-E and 3750 switches connected through their stack ports. For more information about how switch stacks differ from switch clusters, see the “Switch Clusters and Switch Stacks” section on page 6-16.

The benefits of clustering switches include:

•Management of Catalyst switches regardless of their interconnection media and their physical locations. The switches can be in the same location, or they can be distributed across a Layer 2 or Layer 3 (if your cluster is using a Catalyst 3560, Catalyst 3750, Catalyst 3560-E, or Catalyst 3750-E switch as a Layer 3 router between the Layer 2 switches in the cluster) network.

Cluster members are connected to the cluster command switch according to the connectivity guidelines described in the “Automatic Discovery of Cluster Candidates and Members” section on page 6-5. This section includes management VLAN considerations for the Catalyst 1900, Catalyst 2820, Catalyst 2900 XL, Catalyst 2950, and Catalyst 3500 XL switches. For complete information about these switches in a switch-cluster environment, see the software configuration guide for that specific switch.

•Command-switch redundancy if a cluster command switch fails. One or more switches can be designated as standby cluster command switches to avoid loss of contact with cluster members. A cluster standby group is a group of standby cluster command switches.

•Management of a variety of Catalyst switches through a single IP address. This conserves on IP addresses, especially if you have a limited number of them. All communication with the switch cluster is through the cluster command switch IP address.

Table 6-1lists the Catalyst switches eligible for switch clustering, including which ones can be cluster command switches and which ones can only be cluster member switches, and the required software versions.

		Table 6-1	Switch Software and Cluster Capability
		Switch		Cisco IOS Release	Cluster Capability
		Catalyst 3750-E		12.2(35)SE2 or later	Member or command switch
		Catalyst 3750		12.1(11)AX or later	Member or command switch
		Catalyst 3560-E		12.2(35)SE2 or later	Member or command switch
		Catalyst 3560		12.1(19)EA1b or later	Member or command switch
		Catalyst 3550		12.1(4)EA1 or later	Member or command switch
		Catalyst 2970		12.1(11)AX or later	Member or command switch
		Catalyst 2960		12.2(25)FX or later	Member or command switch
		Catalyst 2955		12.1(12c)EA1 or later	Member or command switch
		Catalyst 2950		12.0(5.2)WC(1) or later	Member or command switch
		Catalyst 2950 LRE		12.1(11)JY or later	Member or command switch
		Catalyst 2940		12.1(13)AY or later	Member or command switch
		Catalyst 3500 XL		12.0(5.1)XU or later	Member or command switch
	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
6-2					OL-9775-02