I'm upgrading our network envirnment in the next few months to include a redudant Internet connection. This change is requireing that our ISP switch us from a /30 to a /29. Currently the 3845 router I have in the /30 subnet is the DMVPN hub for our 8 remote teleworkers that have 881 routers in their home offices.
The prepare for this IP address change, my thoughts were to create a new GRE tunnel interface with the new DMVPN hub settings before the IP address change takes place. Once we switch to the /29, the spoke routers should be able to reconnect to our network under the new tunnel interface. We are running EIGRP over our DMVPN, so all routes should change to the new tunnel interface ones the tunnels is up.
Is this the best way to handle this?
Thanks for any feedback!
I don't think there is a better way to handle it than what you plan to do.
Create the new Tunnel with the new IP, once it is able to reach is it will come up automatically and route over that tunnel.
Or ask your ISP to let you hold onto the old /30 space for a week in order to do a graceful migration