Ciscos, BGP, L2TPV3 pseudowires and loopback IPs
up at 3.am
Wed Nov 10 10:20:37 CST 2010
A simpler question(s) than it sounds:
Customer just brought up their first BGP session at a new location. It is
up fine with a full routing table, the second provider hookup is a few
The provider allocated a /24 (x.x.1.0/24) for the network and a /30 for
the PTP connection (x.x.129.172/30). For the initial setup, I did not
configure a loopback, I just put x.x.129.174 on the WAN interface and set
up the neighbor as x.x.129.173. It's working fine.
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.
Using one from the /24 LAN is out unless we subnet it, which we don't want
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?
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
Does this look even close to right? Or do we need another, single routabe
IP from the provider for the loopback? Also, I am assuming we don't need
separate loopback interfaces for BGP as for the Bridge/Tunnel. What about
when the second provider comes up? A second or third loopback to nail up
their WAN IP?
***OR*** is there a way to put their WAN I/F IP on the loopback and take
it off their LAN Ether...and then do IP unnum loop0 on the LAN?
James Smallacombe PlantageNet, Inc. CEO and Janitor
up at 3.am http://3.am
More information about the NANOG