HSRP VLAN migration

[Liam Devine]

Hi,

I've just started working for a new company and while I was getting to grips with their set up I have discovered that our core layer 3 switches, 2 pairs of 4500 switches, are using VLAN 1 for the majority of our servers.

I wish to migrate the address on VLAN 1 to VLAN 2 but I have been asked to minimise downtime. VLAN 1 is currently set up with a HSRP standby address between two of the switches.

My question is, can I assign VLAN 2 on each switch an address on the same subnet as VLAN 1, and then tell VLAN 2 to use the same standby IP address as VLAN 1 so that when I remove the address from VLAN 1, there is no downtime as the virtual IP address still exists?

Or will there be a problem of having one HSRP instance spanning 2 VLANs?

[KenWynWilliams · Accepted solution]

Hi, just to be clear - you want to move SVI on vlan 1 to become a secondary on vlan 2?

If so you'll need to arrange some downtime as the IOS won't allow you to configure the same IP address more than once.

You also need to change all the vlan 1 server access ports to vlan 2 AND any server or other switch trunk ports need to be checked for.

So basically

delete vlan 1 SVI

add vlan 1 addresses and HSRP config to vlan 2 SVI.

change the server access ports to vlan 2

Regards

Ken

[Liam Devine]

Hi Ken,

I basically want to move the SVI to become primary on VLAN 2 and get rid of the config on VLAN 1.

I just wanted to check if I could implement the HSRP config on VLAN 2 before removing it from VLAN 1 to minimise the perceived downtime.

What you are suggesting is the plan I originally came up with but I just wanted to check if there was something I could do to keep the servers online as we would need to send a message to customers telling them that payments would be unavailable even if only for a minute or two (nightmare).

Thanks for your help.

[glen.grant]

   It may bitch about having the same address on two different interfaces .  I would schedule downtime to do this and realistically it should not  take more than 5 minutes. Just cut and paste the configs into the core switches and get rid of old ones , of course saving copies in case of any issues.Of course  that's barring any other issues such as having  vlan 1 trunked to a number of different switches then the window would be considerably longer as you would having to make changes to the trunks .

[Liam Devine]

I told them that the downtime would be minimal so they relented and let me go ahead, in the end the bank system was only off for less than a minute, long enough for the monitor to notice it had dropped off but the processing server itself was oblivious.

Cheers for your input guys.