[c-nsp] Migration from vlan 1 for core.

[Gert Doering]

Hi,

On Tue, Jun 05, 2007 at 02:40:47PM -0400, Jeff Crowe wrote:
> I am planning on migrating a legacy network that utilizes VLAN 1 on Cisco
> devices for it's core network to another VLAN ID (100 in this case).
> 
> Is there any gotcha's that I should be aware of?  All the switches and
> routers have IP addresses that reside in vlan 1, so this may cause me some
> concern and grief...

I'd start by cross-cabling a port currently located in vlan 1 to a port
in vlan 100 - so vlan 1 and vlan 100 effectively form a single big LAN.

Then you can move your devices port by port to the new VLAN (don't forget
"spanning-tree portfast" and enabling vlan 100 on all trunk ports).

If you need to do IP renumbering, this part is a bit more tricky, as 
you'd need to do it in a way that your IGP routing will be happy with 
- maybe having one router with two different interfaces to the same LAN, 
one in the "vlan 1" and one in the "vlan 100" number space, and then
renumber routers one by one (losing adjacency to the "vlan 1" interface
and forming one to "vlan 100").

Finally, remove the cross cable between the vlan 1 and vlan 100 ports...

gert

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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de