PW redundancy

PW redundancy provides redundant links between PEs so that the customer networks can communicate when the path over one PW fails. As shown in Figure 68, PE 1 establishes two PWs (one primary and one backup). The CEs communicate through the primary PW. When the primary PW fails, PE 1 brings up the backup PW and forwards packets from CE 1 to CE 2 through the backup PW. When CE 2 receives the packets, it updates its MAC address table, so that packets from CE 2 to CE 1 also travel through the backup PW. Only static PWs and LDP PWs support PW redundancy.

The MPLS L2VPN determines whether the primary PW fails according to the LDP session status or the BFD result. The backup PW is used when one of the following conditions exists:

• The public tunnel of the primary PW is deleted, or BFD detects that the public tunnel has failed.

• The primary PW is deleted because the LDP session between PEs goes down, or BFD detects that the primary PW has failed.

• A manual PW switchover is performed.