I've got a 4507R with 2 SupII+10GE modules for redundancy. 1 uplink trunk is connected to the 1st module, and another connected to the 2nd module. According to the docs, STP is preserved between Sup-engines, in SSO mode. However, when I pull out the 1st sup-engine to simulate a failed sup-engine, from the console of the 2nd sup-engine, I can see that spanning-tree is in learning mode. Is there any specific configuration I'm missing out to preserve the STP state?
When you have 2 Sup2+'s in your 4k, the first uplink port on each is active. There is no concept of active/standby ports here, so you're depending on spanning-tree to provide redundancy. When you remove the 1st SUP, we lose our STP root, which forces the other link to go through the STP states.
It is up to you to make this process quicker at L2. If both uplinks connect to the same switch, you can put them both in an etherchannel so there will be no loss when a SUP/link is pulled. If both uplinks go to different switches, you want to either look at RSTP or Flexlink for faster convergence.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...