LDP Signaled Pseudowires

MPLS L2Circuits: LDP Signaled Pseudowires

Also called Martini Circuits Defined in RFC 4447

L2VPN and L2Circuit have a lot in common:

• Attachment circuits
• Customer facing interface config
• Same encapsulation
• Dataplane is identical (inner VPN Label, outer Transport label)
• Similar verification and troubleshooting steps
• Both use Martini Encapsulation

LSP creation is separate from the VPN Signalling.

Targeted LDP

LDP between remote PEs (not directly connected)

using loopbacks.

Unlike L2VPN, we dont have auto discovery feature possible because of the use of Route Reflectors (RRs).

With L2Circuits, if a new PE comes up, it. requires manual config on all existing PEs (a disadvantage compared to L2VPN).

LDP Uses TCP/UDP 646

Config:

1. Enable LDP on the loopback set protocols ldp interface lo0.0

2. Configure L2Circuit (this triggers the creation of the targeted LDP session)

3. CE facing interface configu uses either ethernet-ccc or vlan-ccc

set protocols l2circuit neighbor <X.X.X.X> interface <ge-0/0/0.0> virtual-circuit-id X
set protocols l2circuit neighbor <X.X.Y.Y> interface <ge-0/0/1.0> virtual-circuit-id Y

Virtual Circuit ID must match on both sides, similar to site ID in L2VPNs.

Remote PE IP

Local interface

To verify, use show ldp session or show ldp neighbor commands.

show ldp database

Label and Prefix are the two columns that we see in the LDP database.

Input Label Database and Output Label Database

Prefix L2CKT CtrlWord ETHERNET VC 1234

Prefix L2CKT CtrlWord VLAN VC 9876

show l2circuit connections

Packet capture of L2Circuit/LDP

FEC 128

Label Mapping Message in LDP

FEC Elements

Element Type: PWid FEC Element (128)

PW ID: 1234 (Pseudowire ID)

Generic Label (VPN Label)

L2 Circuit does not offer over provisioning.

If we use LDP for transport, for establishing transport LSP, then the FEC advertised is Prefix FEC (2)