CSC - LDP with CE routers

Internetwork Expert Archive

HI,

I have been working through vol1 on sp techs, and have completed the CSC section and although everything works fine I have a question if someone would be good enough to answer;

When you configure ldp on the pe-ce link, ie r2-r1 and r4-r5 in csc setup, since the loopback interfaces of the pe's are not known to the ce routers, then the ldp neigh adj will never become fully operational as it will then use its outgoing serial interface, therefore the ce will not have a /32 host route to the pe ldp router-id, as shown in the following output;

r1#sh mpl ld disco
Local LDP Identifier:
150.1.1.1:0
Discovery Sources:
Interfaces:
Serial1/0 (ldp): xmit/recv
LDP Id: 150.1.3.3:0
Serial1/1 (ldp): xmit/recv
LDP Id: 150.1.12.2:0; no host route

r5#sh mpl ld dis
Local LDP Identifier:
150.1.5.5:0
Discovery Sources:
Interfaces:
Ethernet0/0 (ldp): xmit/recv
LDP Id: 150.1.6.6:0
Serial1/0 (ldp): xmit/recv
LDP Id: 150.1.45.4:0; no host route

Can someone advise what the implications of this are?

Also, on the pe's when you do a show mpls interface, it shows only the pe-pe links as being enabled for ldp, and not the pe-ce?? Do vrf enabled interfaces not form ldp adj's??

Can anyone shed any light on this??

Cheers

Lee

Internetwork Expert Archive

1> The LDP neighbor relationship in this case is established using the pe interface IP address facing the CE router.


2>
The LDP session aswell gets established on the pe-ce link within the VRF instance:

sh mpls ldp nei vrf _____ <<< shows the neighbor in specific vrf instance<br />
sh mpls ldp discovery vrf ___ <<< shows the nei discovery in vrf instance<br />
HTH,
Regards,
Dara