You need to enable MAC reduction (extended vlan range) if you want to support all 4096 STP instances on a 6500. I have personally seen over 3000+ STP instances running using PVST+ with MAC reduction enabled. MAC reduction will steal bits from the bridge priority in order create 4096 unique bridge IDs. The CPU load with PVST+ compared with MST is vary dramatic. As long as you stay away from the older 10/100 Ethernet cards PVST/ RPVST should scale fairly well. I have seen PVST+ start to fail when you reach 75,000 virtual ports and MST can easily handle over 100,000 virtual ports.

Clinton.
[email protected] wrote:
regarding maximum STP instances... I believe theres a platform limit
of 1024 because of the MAC to VLAN bridge mapping on the platform -
but, from the values above, you can see that virtual ports would
hit you quite quickly without appropriate control of the VLANs

alan
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Clinton Work
Airdrie, AB


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