Vlan 1 Migration

[Mokhalil82]

Hi

I am in the process of replacing a core switch. During the process we want to move our vlan 1 to vlan 5 aswel, currently its a server vlan so not ideal as vlan 1

For the migration process I will be connecting the new core to the existing core via 2 links. The new core will have the new vlan 5 on it but the same ip as the vlan 1 ip on the existing core.

So for both to co-exist for the migration process which may take days as we want to migrate bit by bit, I have been advised of this solution

So 2 links between the 2 cores:

Link 1 runs all vlans except vlan 1, and also change the native vlan to another vlan

Link 2 use as an access link with vlan 1 on the existing core side and vlan 5 on the new core side, disable cdp to stop the native vlan messages.

Then we can configure all the vlan interfaces on the new core but leave as shutdown, then as we migrate bit by bit we can shut the svi's on the old and no shut on the new

Is this a good approach, does it seem like it will work

Thanks

[Jon Marshall]

I'm not sure of the logic of what is being proposed.

I don't see how linking vlan 1 to vlan 2 helps you with vlan 5 ?

When you say migration are you physically reconnecting devices connected to the core switch ?

Or are all your devices connected to access switches which then connect to the core ?

When you say migrate a bit at a time do you mean one vlan at a time or a bit of a vlan at a time ?

Jon

[Mokhalil82]

Sorry my mistake, it should be linking vlan 1 with vlan 5, ive amended the above post.

All devices are currently connected to access switches and then into the core. 

We want to move only layer 2 first in chunks. so the physical links and the svi's. Once we are ok with that we then want to migrate L3 links which willbe the routed links to the firewalls and other site. 

The existing vlan 1 is currently a server vlan but on the new core we want vlan 5 as the server vlan but with the same subnet. So someone (more knowledgeable than myself) suggested the above approach to extend the broadcast domain but this will also allow vlan 1 and 5 to coexist with the same subnet

Thanks

[Jon Marshall · Accepted solution]

Okay that makes more sense.

So as you move access switches you keep the existing SVIs up until all devices within a vlan are now connected to the new switch and then you shut the old SVI down and bring the new one up with the same IP address.

If you do this be aware that the clients arp cache will still have the old mac address of the existing SVI mapped to the IP address not the mac address of the new SVI.

You would need to either clear the arp cache on all clients in that vlan once you switch to the new SVI, do it in the evening and allow the arp cache to timeout for users in the morning or simply reboot the clients.

Any one of the above would work

In terms of vlan 5 it should work but I can see no need for it to be allowed across the trunk link that allows all vlans because vlan 5 doesn't exist on the old switch.

It should work with the proviso of clearing the arp cache.

Personally I would just move the servers across and leave them in vlan 1 until they are all on the new switch and then simply create vlan 5 with it's SVI and allocate the server ports into that vlan.

With the "int range .." command it should be fairly quick to do.

You are going to have to clear the arp cache anyway.

But yes what you are proposing should work.

Jon

[Mokhalil82]

Thanks Jon, I was thinking about the arp issue and this is something we will do out of hours so enough time for arp to timeout

[Nuhu_2007]

Dear Jon Marshall,

Just see your comments on migration of Servers from Default VLAN to New VLAN , We did the same as you have mentioned i-e have created a new vlan 10 for Server ,remove  Vlan 1 SVI and have assigned to Vlan 10 .

Now we are facing problem with some of Application Servers during peak working hour the client PC hang for a while . We need to find it is there any further steps required or no as we troubleshoot every thing from Network side , no ping drop, no CRC etc are observed .

Please guide your prompt reply will be appreciated.

attach file  can help in sorting out issue.

Regards

[Amafsha1]

Why did you not like VLAN 1?