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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 6 Clustering Swit ches Planning a Switch Cluster

Virtual IP Addresses

You need to assign a unique virtual IP address and group number and name to the cluster standby group.
This i nf ormat ion m ust be co nfigured on the m ana gem ent VL AN on the a ctive command sw itch. T he
active command s witch re ceives traffic destined for the vir tual IP addre ss. To manage the cluste r, you
must access the activ e command switch through the virtual IP address, not through the command-switch
IP address. This is in case the IP address of the active command switch is different from the virtual IP
address of the clust er st and by grou p.
If the active command switch fails, the standby command switch assumes ownership of the virtual IP
address and becomes the active command switch. The passive switches in the cluster standby group
compare their assigned priorities to determine the new standby command switch. The passive standby
switch wi th the highest p riority t he n beco mes th e sta ndby com ma nd sw itch. Whe n th e previously activ e
command switch be comes ac ti ve ag ain, it res umes its r ole as t he acti v e command swit ch, and the curr ent
active comman d s wit ch b ecom es th e st andby c om mand swi tch agai n. For m ore i nfor ma tio n ab out IP
address in switch clusters, see the “IP Addresses” section on page 6-15.

Other Considerations for Cluster Standby Groups

These re quirem ents also apply :
•Standby command switches must meet these requirements:
–
When the command switch is a Catalyst 3550 switch, all standby command switches must be
Catalyst 3550 switc hes.
–
When the command switch is a Catalyst 2950 switch running Release 12.1(9)EA1 or later, all
standby co mm and s wit che s m ust b e Ca talyst 295 0 swit ches ru nning Rel ease 12. 1(9 )EA1 or
later.
–
When the command switch is a Catalyst 2950 switch running Release 12.1(6)EA2 or later, all
standby co mm and s wit che s m ust b e Ca talyst 295 0 swi tches ru nning Re le ase 1 2. 1(6)E A2 or
later.
–
When the com mand switc h is runnin g Release 12.0(5 )WC2 or ea rlier, the standby comman d
switches c an be t hese swit ches: C atal yst 2900 XL, Catal yst 2950, and Cat alyst 3500 XL
switches.
We strongly recommend that the command switch and standby command switches are of the same
switch platform.
–
If you have a Cataly st 3550 co mm an d swi tch, t he sta ndby com ma nd switche s sh ould be
Catalyst 3550 switc hes.
–
If you have a Cataly st 2950 co mm an d swi tch, t he sta ndby com ma nd switche s sh ould be
Catalyst 2950 switc hes.
–
If you have a Catalyst 2900 XL or Catalyst 350 0 XL command swi tch, the standby comma nd
switches should be Catalyst 2900 XL and Catalyst 3500 XL switches.
•Only one clust er stand by group can be assigne d to a cluster.