Migrate from Cisco Nexus 5596 to Cisco 93180YC-FX and keep same four FEX online!

End user wants to migrate from a pair Nexus 5596 L3 (vPC) with four FEX to Cisco 93180YC.

Once the migration is complete in Q3 later this year they can pull the FEX out and use more 93180YC as ToR (Top of Rack switches)!

Are the hosts connected to the FEX's redundant? As in each host connected to a pair of FEX's? Then it‘s easy, run the n9ks parallel to the 5ks with their own vPC domain. Disconnect A-side FEX's, connect them to the n9ks and bring them online. Failover hosts to them, repeat with B-side. No downtime if your redundancies work.

If the hosts are not redundant, then it‘s impossible to do it without downtime. Same process though. Downtime would be equal to fex down, unplug at n5k, connect to n9k, online procedure.

Either way: pre-provision the FEXes and all needed config on the n9ks, before you disconnect them from the n5ks. That way you can even add FEX interface config to the n9ks without having had a FEX ever connected to them.

Obviously don‘t connect a Fex to both an n5k and n9k at the same time. Best case: it won‘t work. Worst case: your vPC domains will go offline, downing everything!

Since L3 is configured on the 5k and vPC synchronization is not supported between different models no matter what vPC domain you configure, you would basically need to build parallel and have a hard failover.

We lifecycled our N6K’s to N9K’s back in 2021 and that was simply the easiest solution.

That or get rid of any vPC and go back to simple port channels with different spanning tree values per switch , basically take down the vPC

However your L3 can only be active on 1 side anyway so I’d say prepare as much as possible and get a maintenance window with down time.it would be possible to build l3 in parallel, if it‘s running HSRP/VRRP. L2 migration link between 5k and 9k, shut the SVI on backup 5k, no-shut on backup 9k, migrate, failover and move active SVI to 9k...

All ESXi hosts are redundant on the FEX's. Thanks, thats what I had in mind along with the other comments with a separate vPC domain.

Are you using Jumbo Frames with ESXi?

9300 EX and FX don't need policy maps for jumbo frames anymore. Interface commands work just fine!