Core Router Upgrade Best Practices

[jesse.garcia11]

We will be updating our Core Routers this summer and after extensive research, I have found some good info but would like to know if anyone can provide some experience or recommendations of their own. We are a start topology campus, with 1 core Cisco 6509 at our main office, and 5 core/distribution 6509's at remote sites that come here to the main core via fiber. Each Distribution/Core has about 40-60 switches of their own at each site. So we will be upgrading just the 6509s, 6 total. We will be upgrading to Catalyst 9606s. Here is what I have gathered so far:

1. schedule maintenance window (MW)  durring a night or a weekend.

2. preconfigure everything on cat4k before MW

3. prepare all cables - be sure that they're long enough, you have correct sfp moules etc...

4. write exact step-by-step plan with timing - sequence of cables that will be reconnected, sequence of tests that will be performed after reconnecting to confirm that everything is up

5. during MW follow the plan

6. confirm that everything works

My initial plan was to make a virtual environment with our current configs, then just replace it with the new one. But Eve-NG requires purchasing the images for the nodes. 

Is there anything else to try to test in house before deployment? 

We do expect errors, and will be scheduling a good size MW. But want to limit as much as possible with testing in house. 

Any help appreciated. Thanks

[MHM Cisco World]

One idea here 
Cat6K support VSS, so if you config VSS then you must keep in mind that config Cat9K as stack

[jesse.garcia11]

Oh  Thank you! I did forget to mention that as well. We do have VSS here at the main site So that will need to be a stack? No longer considered VSS?

[MHM Cisco World]

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9600-series-switches/guide-c07-742784.html

this whitepaper can help you. 
MHM 

[paul driver]

Hello
Can you elaborate on this migration, I assume give the size of the topology you would be wanting to introduce this new network alongside the current existing production network and migrate piecemeal ( all L2 interconnect first, then  L3 routing) ?

[Flavio Miranda]

Hello,

  This link is very cool "Migrating from Cisco Catalyst 6500/6800 to 9600 Series Switches"

https://www.cisco.com/c/en/us/products/collateral/switches/catalyst-9600-series-switches/guide-c07-742784.html

If I were to add something on your migration strategy I would focous on the coexistence phase while deploying the boxes. Maybe it would be a good idea do not use a "big bang" strategy but replace one box at a time and in different window. Maybe a week or two between window. If you were hit by a bug, you would affect only on site and not all at once.

  Also, maybe transfer all the layer2 work to the new switch first and leave the layer3 migration to a second phase. Of course, it would required space to keep both devices running at the same time.

[jesse.garcia11]

Thank You Flavio. Yes I forgot to mention that as well.. We will be doing one site at a time, with our main site being last. Space is an issue for us as well. But I will be looking over the link. Thanks again.