I have a simple setup - two core switches (8800s), several edge switches (460s) connected like this: 8800s are running 126.96.36.199-patch1-9, 460-1 is on 188.8.131.52, 460-2 is on 184.108.40.206.
My problem is that the 460s are on 1GB fiber (ports 55,57) and I need to upgrade them to 10GB while everything stays up and running, i.e. the devices connected to the 460s don't lose access to the network.
The end goal is that the 10GB uplinks also need to be in ports 55,57 (for sanity's sake) Ideally, the corresponding ports in the 8800 should also stay the same (sanity!), but I could be persuaded to use different ports.
If I understand correctly, I can't just replace the SFPs one by one because of port speeds and sharing configs/mismatches.
Physically, the two 460s are right on top of each other, so I could run something between them and use that as an alternate path, but I also hear that loops are deadly. I don't think I can easily define that as a 460-ISC MLAG, as I'd have to put the ports on the 8800 side into sharing mode, affecting vlan-port associations to the 460. (Let's say vlan 1 goes to 460-1 vlan 2 goes to 460-2, let's say on the 8800s port 1:11 goes to 460-1, port 1:12 goes to 460-2. What all would die if I group 1:11 and 1:12? At least all vlans pointing to 1:12 would have an issue, right?)
On the other hand, I'm not currently running spanning-tree. If I connect the 460-1/2 with a gig-ether (or two , shared) in a non-MLAG setup, make sure all vlans that exist on both switches are defined to go to to both switches (and the connection between the 460s) and define spanning-tree on all the vlans, would that get me to a point where I can just rip out one 460's fiber uplink, replace it with 10G, then do the other 460, then disconnect the link between the 460s and kill off STP?
I've never configured STP on Extreme switches, btw. Especially not with share groups and an MLAG.
So, how can I pull this off without downtime (or downtime in the "few seconds" range)? Would STP be viable? Is there something better I can do during the fiber/SFP replacements?
Thanks for your help!