Router-on-a-stick swap to L3-switches

[j_saarikko]

Hi Gents,

My very first post to any forum that relates my work... I was not able to find any discussions about this, so sorry if this is answered somewhere.

Question goes, is there any best practices or things that should be taken in to an account when one is going to swap ROAST devices to L3 capable switches.

So, my task is to update redundant CE devices (2 x 1800 series router and 2 x 2960 switches, Router on a stick) to some L3 -switches. I think that this is quite straight forward to do. You just swap one side at time. But, if you try to minimise or even avoid network connectivity lost, what to do?  We use naturally HSRP and spanning tree. Is there anything to pay a special attention?

I think that HSRP timers are default. We use RSTP. Behind the switches there are some servers with dual NICs, but its only fault tolerance, not load balancing.

Thanks!

[dukenuk96 · Accepted solution]

Hello!

Well best practice - do not hurry and do everything not at once, but by little iteration steps. Begin by adding new L3 switches to existing network without connecting to them any production servers. Then move IP interfaces one by one from ROAST to L3 switches. Plan everything on a paper or any documenting solution up to the exact commands you going to execute on each peace of your network. Take advantage from peer review tradiotion with your co-workers. If you are not very confident with what you are going to do, simulate it all in Packet Tracer/GNS/IOU/etc.

Your network is not large as it seems from your description, so I think you will do everything within two or three weeks without any impact on production.

[j_saarikko]

Hi,

thanks dukenuk96. There were good hints indeed. So, I replace reduntant router first with L3 switch and make it pair for another ROAST. If it works I'm able to replace another router with second L3 switch and if HSRP works I'm able to swap IP interfaces from old L2 switches to new L3 switches. I think I got it..?

This part of the network is not very big but very critical anyway :)

Demo with actual devices was on my mind and might reveal some issues and practices for me.

Thanks a lot!

[dukenuk96 · Accepted solution]

It depends on your actual topology and current configuration, but I think for you will be even possible to place new L3 switches as an extent to existing HSRP groups. After accurate verfications you will be able to remove old equipment one-by-one without any visual impact on you production services.

Good luck!