[c-nsp] VTP/STP/TRUNK

[Boštjan Fele]

Hi,

If you have a lot of VLANs (more than switch can have STP instance for) migrate to MSTP config from PVST+ spanning tree. I had similar problems that VLANs were not pruned even when pruning was enabled and no access ports were on edge switch...

Regards,
Bostjan

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Shaun
Sent: Sunday, December 18, 2005 9:55 AM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] VTP/STP/TRUNK

I have a 3750 connected to multiple 2950G's, 3750 is running as VTP Server
V1 with pruning enabled.  The 2950G's are trunked to the 3750 and run VTP as a client.  One of my 2950G's recently through this error at me.

%SPANTREE_VLAN_SW-2-MAX_INSTANCE: Platform limit of 64 STP instances exceeded. No instance created for VLAN153 (port Fa0/1).

I understand the error, STP is enabled on too many interfaces for this device but this switch only has probably different vlans assigned to it. 
After further investigation I found that a sh int <port> trunk on both the 2950 and the 3750 showed different info.

2950G
    Port        Vlans in spanning tree forwarding state and not pruned
    Fa0/1       1-2,20,50,60-61,95-119,121-153,155-158

3750
    Port        Vlans in spanning tree forwarding state and not pruned
    Fa1/0/13    1-2,60,97-99,115,120,122,133,137-138,141-142,144,153

As you can see the 2950 is showing more vlans on the trunked port than the 3750 is showing.  Is this normal?  Shouldn't they match?

Just to clarify I'm not restricting vlans on the trunked interfaces on the 3750.

I also ran this same test on a different 2950 that's trunked to the 3750 and the results where backwards on that switch.  The 2950 showed fewer vlans on the trunked port than the 3750 showed..

I verified I have the right ports to the right switches by doing a sh cdp nei

Thanks in advance.

-- 

~Shaun 



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