migrating class b lan to class c

[chrisgerke]

I work for a very old company that owns a class B IP range. I've been given the task of moving our lan addresses to class C.

I was going to start with the following approach;

- create a new dhcp pool on existing win 2008 server with class C range

- create new corresponding vlan/subnet on switches with dhcp relay

- create new corresponding svi for the clan

- update GRE/ASA configs accordingly

Does this seem like the correct approach?

It is my understanding that dhcp "just works". So the two separate vlans/subnets should only get dhcp leases from their corresponding pool on my win 2008 server?

Thanks in advance.

[Richard Burts]

Assuming that the DHCP scopes are configured correctly then yes each vlan should get addresses from its own scope.

In general the approach that you describe sounds reasonable. I am not entirely clear what is involved when you talk about GRE/ASA. Would providing for address translation for the new subnet be part of that? And I do not know enough about your network to know whether there need to be changes in routing protocols to create routing table entries for the new subnet.

HTH

Rick

[chrisgerke]

The ASA/GRE part refers to our wan. Basically traffic flows like this;

Workstations > Core > ASA > INTERNET

OR

Workstations > Core > ASA > GRE > INTER-OFFICE

We have GRE for VPN tunnels.

[rfalconer.sffcu]

I did a major IP address change at a large hospital. Your plan should work fine. It's pretty easy to get the endpoints migrated too. Just copy paste on the interface something like:

shut

switchport access vlan

no shut

The shut/no shut will cause the endpoint to send a dhcp request and get an address on the new subnet.