Core Switch Migration (HPE to Cisco Nexus)

[Dzaky Azfa]

I want to change my Core Switch (1 HPE Switch) into using 2 Nexus 9316D-GX and configure them as vPC. What is the best practice to migrate from using HPE to my new Cisco Nexus (vPC) . The existing condition is my core switch connected to 4 ToR Switch that each ToR connected to Server and Storage. 

Is there any advice to do this migration scheme? any advice would be very helpfull, thank you

[Elliot Dierksen]

Do you have a diagram or can you provide more information about your topology? It is hard to make a useful recommendation without more information. Are you planning a flash cutover or are you trying to do it in phases and minimize downtime? That latter will be difficult, but you may be constrained by availability requirements. The other big thing to think about now is your test plan. Identify your key applications and how you will go about verifying that they are working correctly after the change. Otherwise you could have a troubleshooting nightmare. Do you have any spare equipment where you could lab this up?

[Dzaky Azfa]

Here is my proposed topology and existing. I wish to be able to migrate it without downtime, if you have any suggest to do it without downtime it would be very helpful. but if you have other idea with very minimum downtime

[Elliot Dierksen · Accepted solution]

I am assuming the HPE is the default L3 gateway as well as the aggregation point for the cabling. Based on that, I can't see any way to do that without down time. Is your drawing physical or virtual? You only have 1 line from the core switch to each ToR switch. You will need 2 (minimum) in a vpc pair (1 to each member), and you should use LACP for that. Another problem you would have trying to do it without down time is HPE uses MST (single spanning tree for all VLAN's) where Cisco uses PVST (spanning tree instance for each VLAN). You could mount the new switches and run the cables (don't connect to ToR switches until cutover) in advance to minimize the down time.

[Dzaky Azfa]

Dear Mr. Elliot,

after reading this i got an idea to migrate it. so first of all im gonna install and configure nexus vpc on both nexus and the connect it to existing core switch (as temporary L2 link) & my upstream (L3 connection/device). and then i will move the connection from the access switch one by one. when it is done i will set any L3 protocol at my nexus (as my new core switch) such as L3 gateway, Routing, etc. after that i will cut my Temporary L2 Link connection and remove my old core switch from my upstream

[Elliot Dierksen]

Excellent! You can do the L2 and L3 migration separately as you are planning. Once you have L2 connectivity between the old core and new nexus core, you could move the L3 prior to completing all the L2 migrations. It all depends on your preference. Either way you can minimize the downtime by figuring out a way to break the migration up into smaller pieces. Don't forget to have some kind of test plan (even if it is very informal) so you can be sure everything is working as expected after each change.

[rais]

Apparently Nexus 9316-D do support MST.
Regards.

[Elliot Dierksen]

OK, but all my other concerns still stand. If you aren't planning to interconnect with other HPE gear, I would leave the Nexus on PVST.