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C2950: Spanning-tree

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A customer hads lots of Cisco 2950 switches. They can support hundreds (perhaps thousands) of VLANs. We use VTP and that supports 250 VLANs. We use 'spanning-tree mode pvst' which can create a spanning-tree instance for 64 VLANs. From the 65th VLAN onwards we get this line added to the 2950 config:

no spanning-tree vlan 43,120,132

We presume that is is because PVST on the 2950 can only handle 64 VLANs.

would like to know if this will cause problems for the 65th, 66th, 67th VLANs? We do not put loops in the network at present.

Should we use a different spanning-tree mode?


Re: C2950: Spanning-tree

In most cases all vlans are not needed on the trunk links. "Manually" prune off all unneeded vlans on the trunk "switchport trunk allowed vlan xx" . This will get rid of that message . This does not affect what the vtp server is sending to the switches. What you are seeing is a 2950 hardware restriction and any vlan above 65 has no spanning tree running on the vlan on the switch . By pruning off unneeded vlans this reduces the spanning tree instances needed on the switch.

Community Member

Re: C2950: Spanning-tree

If you are 100% positive that there is no chance for loops than this is really a non-issue:)

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