e.
We will need to set up a L2TPV3 tunnel to their old location (single homed, no BGP on that side). Upon initial reading of Cisco docs to do this, we will need a routable IP on a loopback interface for starters.
I'm pretty sure this is just a recommendation based on good practise (routeability to endpoints), I'm sure since you are not multihomed you can just use "ip local interface WAN1" and be done with it, I seem to remember doing something similar in an l2tpv3 pw class and it working.
Using one from the /24 LAN is out unless we subnet it, which we don't want to do.
So the question is, can I just "move" the PTP IP address x.x.129.174 from the WAN interface to the loopback like this?
interface Loopback0 ip address x.x.129.174 255.255.255.252 (that's the mask we're using on the WAN- Cisco's loopback examples show .255)
interface WAN1 (actually a gigether) ip unnumbered loopback0 (or no ip addr?)
neighbor x.x.128.173 update-source Loopback0
No, if you were to do this you should get a new transfer network, you can't have the same address on two interfaces (and in fact, you should really be stealing an address from your internal /24 which doesn't require any re-subnetting (if you are happy for this address to be unreachable) and it should have a /32 mask... -- David Freedman Group Network Engineering Claranet Group