Cisco WS-C3750-48PS-S Software Configuration Manual page 143

Chapter 6 Clustering Switches
Table 6-1 Basic Comparison of Switch Stacks and Switch Clusters (continued)
Switch Stack
Stack master is the single point of complete management for
all stack members in a particular switch stack
Back-up stack master is automatically determined in case the
stack master fails
Switch stack supports up to eight simultaneous stack master
failures
Stack members (as a switch stack) behave and is presented as
a single, unified system in the network
Integrated management of stack members through a single
configuration file
Stack- and interface-level configurations are stored on each
stack member
New stack members are automatically added to the switch
stack
Recall that stack members work together to behave as a unified system (as a single switch stack) in the
network and are presented to the network as such by Layer 2 and Layer 3 protocols. Therefore, the
switch cluster recognizes switch stacks, not individual stack members, as eligible cluster members.
Individual stack members cannot join a switch cluster or participate as separate cluster members.
Because a switch cluster must have 1 cluster command switch and can have up to 15 cluster members, a
cluster can potentially have up to 16 switch stacks, totalling 144 devices.
Cluster configuration of switch stacks is through the stack master.
From the CLI, you can configure a switch cluster to contain up to 16 switch stacks. However, from CMS,
Note
the maximum number of actual devices in a switch cluster is 16, irrespective of the number of devices
in switch stack cluster members. For example, if a switch stack contains three stack members, they are
counted as three separate devices.
If you used the CLI to configure a switch cluster that contains more than 16 actual devices and then try
to display the cluster from CMS, CMS requires you to remove cluster members until the CMS limit of
16 is reached.
These are considerations to keep in mind when you have switch stacks in switch clusters:
•
•
78-16180-02
If the cluster command switch is not a Catalyst 3750 switch or switch stack and a new stack master
is elected in a cluster member switch stack, the switch stack loses its connectivity to the switch
cluster if there are no redundant connections between the switch stack and the cluster command
switch. You must add the switch stack to the switch cluster.
If the cluster command switch is a switch stack and new stack masters are simultaneously elected in
the cluster command switch stack and in cluster member switch stacks, connectivity between the
switch stacks is lost if there are no redundant connections between the switch stack and the cluster
command switch. You must add the switch stacks to the cluster, including the cluster command
switch stack.
Switch Cluster
Cluster command switch is the single point of some manage-
ment for all cluster members in a particular switch cluster
Standby cluster command switch must be pre-assigned in case
the cluster command switch fails
Switch cluster supports only one cluster command switch
failure at a time
Cluster members are various, independent switches that are
not managed as and do not behave as a unified system
Cluster members have separate, individual configuration files
Cluster configuration are stored on the cluster command
switch and the standby cluster command switch
New cluster members must be manually added to the switch
cluster
Catalyst 3750 Switch Software Configuration Guide
Planning a Switch Cluster
6-15