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Migration VSS to C9600 Stackwise best practices

Hi everyone,


I'm actually studying how to migrate our old VSS to a new C9600 Cluster using stackwise. We want to migrate in the smoothest way if possible.

Our network is design as follow:


VSS to Stackwise.png



All the default IP address are on the VSS for each Vlan and all access switches are connected through LACP with a connection on each C6500. What is the best way to interconnect the old VSS and the new Stackwise to progressively migrate the access switch and then move the default ip address from old to new ?


Is there somewhere a best practices guide ?




Hervé Jacquemin



Leo Laohoo
VIP Community Legend

There will be an outage because the downlinks (to the access switches) will need to be switched across to the new pair.

As Leo stated there will be a hit but i was able to minimize mine doing it like this if it helps , there is no whitepaper on this just on moving from standalone to VSS that i have seen anyway , no VSS to VSS migration doc , I would do this in a shut down scenario its cleaner

To do this live too the FW would need a connection to the 9600 too , so when your migrating traffic doesnt just fall off when its moved to the 9600 side , the path upstream needs to be there too at same time on both clusters

1 create a replication of all layer 2 vlans and SVIs on the 9600 that are on the 6500 cluster keep them in shut down state , make sure its identical both setups

2 Create layer 2 trunk connection between both VSS clusters allow all vlans

3 Take 1 vlan as a test , get a pc on it at access layer ping right up through an past its GW so you know path is ok keep the ping running

4 Shutdown the SVI on the 6500 side and instantly bring it up on the 9600 cluster at same time , ping drop should only be like 1 or 2 if its done right.

5 Repeat the process for each SVI until all layer 3 interfaces have been moved over and the 9500 is the doing the routing , 6500 becomes a layer 2 VSS

6 Now you need to move the access layer link from cluster 6500 to cluster 9500 , what you can do to minimize it depends on spare ports , if the access switch has free ports ,create a secondary set port-channel but connect it to the 9600 cluster keep it in shutdown state and set the STP cost on each end to something really high 1000000 , make sure switches are in some form of rapid stp so the convergence is quick at layer 2

7 Once your happy with the config and STP is in place you can bring up the secondary PO it wont do anything due to the STP cost but as soon as you shut down say port-channel A it will bring up the only other valid weighted path STP port-channel

Thats off my head how i did it the last time , i would map out every task and possibility that could go wrong when doing this live before touching it , best approach if possible shut it down and move it over in a mntc window, a lot more can go wrong trying to do this live

We think to do something exactly like that at the difference we would first keep the default gateway on the old VSS and as soon ass all access switches have 1 link on the new vss and working find, move the default gateway on the new VSS.

But it's clear we have to test this as first step, but I'm thinking the same. An outage of "2 pings" is not really an outage for me :)
Thanks both for your input.