How many STP instances are supported on 6500 IOS

[yueric]

I know that 2950 switch can support up to 64 STP instances,but how many instance for 6500?

A situation is I had cerated vlans exceeding 64 on 6509 works as vtp server,it's ok with 6509,but there're many vtp clients which are 2950.The running-config shows "no spanning-tree vlan XXX"automatically.I know it's the limitation for 2950,and it seems I have to stop spanning-tree for some vlans.So,I'm afraid of 6509 has spanning-tree instance and 2950 has not for vlans ,will it come up unexpected action.Any replay will be very appreciated.

[Georg Pauwen]

Hello,

The maximum number of Per VLAN Spanning Tree instances on the 6500 switch is 128. In your case, after you grow past 64 (or 128) VLANs, you will need to configure MSTP and begin grouping VLANs into common Spanning Tree instances. The 2950 and the 6500 both support MSTP, you might want to check these links for a detailed description on how to configure it:

Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide, 12.1(14)EA1

Configuring MSTP

http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a00801a6ba7.html

Catalyst 6500 Series Cisco IOS Software Configuration Guide, 12.2SX

Configuring STP and IEEE 802.1s MST

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a0080160a5b.html

HTH,

GP

www.solutionfinders.nl

[yueric]

Thanks for the reply so much,but how do you know the STP instance limitation of 6509 is 128?You experienced this before or you could suggest me how to get an official doucment.Because I may need to a document to prove this when I'm going to discuss this problem with my customer.And the switches are all production,so,it's not possilbe to change the entire sapnning-tree mode right now.But it's possible to change a part of spanning-tree mode in the near future.Before doing this,I have to confirm another situation is that PVST and MST can exist in a network simultaneously?

[milan.kulik]

Hi,

I don't beleive the limit is 128.

There always 2 STP instances on 6500s.

The number of "active logical STP ports" is being limited on these high-eng switches.

See http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Dpass_through%26location%3Doutline%40%5E1%40%40.ee97145/51#selected_message

and following thread for detailed "Ask the Expert" discussion.

"...Catalyst 6500/6000 formula number of ports (number of trunks * number of VLANs on trunks) must be less than 4000 for Supervisor Engine 1 and 20000 for Supervisor Engine 2."

See http://www.cisco.com/en/US/customer/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml

You can also earch "number of trunks" in this document

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/ol_4164.htm#wp16976

or ReleaseNotes proper to your IOS.

Regards,

Milan

[j-craven]

That's incorrect. I've got 6500s running over 200 rapid-pvst+ sessions right now.