VPLS with LDP and BGP
Load basic.vpls.ldp.init.cfg
The CE routers CE1-3 are preconfigured with EIGRP.
Configure VPLS and verify that the EIGRP neighborships come up.
Use LDP for the signaling of the service label, but do not manually specify neighbors under the VFI.
Use R4 as the RR for VPLS services, using ASN 65000
Answer
Explanation
To ease the configuration burden from the requirement for a full mesh of tLDP pseudowires, we can use BGP autodiscovery. This works by using the BGP l2vpn/vpls AFI/SAFI. In this lab we used R4 as our RR, but the RR placement is arbitrary.
All routers now use the autodiscovery bgp signaling ldp statement under the VFI instead of providing a list of all remote PEs. This causes the router to advertise a BGP l2vpn/vpls route that looks like this:
The RD, RT and AGI (Attachment group ID) are all auto-generated in the format <ASN>:<VPN ID>
The router uses the nexthop of the update as the endpoint for the pseudowire, and the VPN-ID portion of the L2VPN AGI as the VPN ID. The L2VPN RID (which can be manually configured using l2vpn router-id x.x.x.x) is used as the prefix in the NLRI, but this isn’t used as the endpoint for tLDP. The nexthop of the route is used as the endpoint for tLDP.
The RD keeps multiple BGP updates from the same PE unique, and the RT only imports routes that match the particular VPLS VFI. The labels advertised in BGP are not used, because the service label will be learned via the tLDP session. The VPN ID, extracted from the L2VPN AGI, is used as the VCID. This must match between all PEs, even if you use different RTs to constrain the VPLS topology.
There is a slight difference in the LDP FEC when BGP autodiscovery is used. The FEC type is 129 instead of 128. This contains some additional parameters such as the source (1.1.1.1 below) and target (3.3.3.3) below.
The data plane is the same as before. The difference is just that participating PEs are discovered via BGP instead of manually configured on each router.
You can still add manual neighbors under the VFI when autodiscovery is used. However, both sides of the pseudowire must be defined manually, since the manual neighbors use FEC 128 instead of FEC 129.
Verification
Verify that EIGRP neighborships are up on the CEs and that the loopbacks are known via EIGRP.
Verify the psuedowires are up and that MACs are learned on the PEs:
Verify the RD, RT and VPLS IDs that were auto-generated:
Verify the labels for the pseudowires. We can see those very high label values seen in BGP are not used:
We can use the following command to discovery autodiscovered psuedowire peers:
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