STP Limits on 6500

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Sep 5th, 2010
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Anyone know what is the RAPID-PVST+ limitation on a 6509 with VSS?  I know its based on chassis limits, but with 12.2SXI, what is this limit? I have heard 10,000, and i have heard more... Any clarification would be great :-)


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Reza Sharifi Sun, 09/05/2010 - 19:24
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Per vlan spanning tree (PVST) is based on the number vlan and the maximum number of vlan on a 6500 is 4094.



ct_yau Wed, 12/01/2010 - 06:49
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I'm afraid 4094 is not the answer.  Cisco 2960 series switches support 255 VLANs but only 128 number of spanning-tree instances.  I reached the limit once.  Instead of not allowing me to create new vlans the switches silently disabled STP for the new VLANs.  It created bridging loops and killed me.

I am also looking for the maximum number of spanning tree instances on 6500 to avoid dying again but have not found an answer and reached here.

MST is safer than PVST but unfortunately PVST is the default on Cisco.  I have a network of over 200 switches and it is difficult to switch to MST.

Shashank Singh Wed, 12/01/2010 - 07:12
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The maximum logical interfaces for Per VLAN Spanning Tree Plus (PVST+) is 1800 for each module and 13,000 total for the switch. The show spanning-tree summary totals command displays the number of logical interfaces in the STP Active column.

The only way around this is to run Multiple Spanning Tree (MST) versus PVST, which has different limits:

  • PVST+ 13,000 total 1,800*/slot

  • RPVST+ 10,000 total 1,800*/slot

  • MST 50,000 total 6,000*/slot

Otherwise, pruning unnecessary VLANs from trunks is the best way to reduce the number of logical interfaces on a module or switch. But, regardless of STP mode, 10 Mbps, 10/100 Mbps, and 100 Mbps switching modules support a maximum of 1,200 logical interfaces per module.

Hope this helps!


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