We have a layer 3 campus, so all of our access switches are running VLAN interfaces which act as the gateway for each VLAN. From there, traffic is routed upstream.
We're replacing an old Cat6500 with a Cat9400 soon. The 9400 will need to have the same gateway IP as the 6500, and I'm trying to move away from a hard cut and do something a little more graceful in terms of outages. A lot of these devices have static IPs and gateways configured, so unfortunately I can't just come up with new DHCP scopes and start patching.
I'm wondering if anyone here has used VRRP for this purpose, i.e. setting the shared IP to the actual gateway IP for each VLAN, configuring the new switch as standby, and then moving devices over to the new switch and shutting down the VLAN interfaces on the old switch as we go. When everything is patched into the new switch, set the VLAN interface IPs to match the gateway IP and then remove the VRRP config.
I tested this out in GNS3 and it seems to work fine, but that is small-scale and might not be representative of some weird problems that could pop up, i.e. ARP conflicts and such.
Anyone here have experience doing something like this with access switches? Any tips for not blowing everything up?
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