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Catalyst 2940 Switch Software Configuration Guide
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Chapter 5 Clustering Switches
Planning a Switch Cluster
IP Addresses
You must assign IP information to a command switch. You can access the cluster through the
command-switch IP address. If you configure a cluster standby group, you must use the standby-group
virtual IP address to manage the cluster from the active command switch. Using the virtual IP address
ensures that you retain connectivity to the cluster if the active command switch fails and that a standby
command switch becomes the active command switch.
If the active command switch fails and the standby command switch takes over, you must either use the
standby-group virtual IP address or the IP address available on the new active command switch to access
the cluster.
You can assign an IP address to a cluster-capable switch, but it is not necessary. A member switch is
managed and communicates with other member switches through the command-switch IP address. If the
member switch leaves the cluster and it does not have its own IP address, you then must assign IP
information to it to manage it as a standalone switch.
Note Changing the command switch IP address ends your CMS session on the switch. Restart your CMS
session by entering the new IP address in the browser Location field (Netscape Communicator) or
Address field (Internet Explorer), as described in the release notes.
For more information about IP addresses, see Chapter 4, “Assigning the Switch IP Address and Default
Gateway.”
Host Names
You do not need to assign a host name to either a command switch or an eligible cluster member.
However, a host name assigned to the command switch can help to identify the switch cluster. The
default host name for the switch is Switch.
If a switch joins a cluster and it does not have a host name, the command switch appends a unique
member number to its own host name and assigns it sequentially as each switch joins the cluster. The
number means the order in which the switch was added to the cluster. For example, a command switch
named eng-cluster could name the fifth cluster member eng-cluster-5.
If a switch has a host name, it retains that name when it joins a cluster. It retains that host name even
after it leaves the cluster.
If a switch received its host name from the command switch, was removed from a cluster, was then added
to a new cluster, and kept the same member number (such as 5), the old host name (such as eng-cluster-5)
is overwritten with the host name of the command switch in the new cluster (such as mkg-cluster-5). If
the switch member number changes in the new cluster (such as 3), the switch retains the previous name
(eng-cluster-5).
Passwords
You do not need to assign passwords to an individual switch if it will be a cluster member. When a switch
joins a cluster, it inherits the command-switch password and retains it when it leaves the cluster. If no
command-switch password is configured, the member switch inherits a null password. Member switches
only inherit the command-switch password.