Alcatel-Lucent 7750 SR OS - Dual Homing to a VPLS Service; Figure 40: Dual Homed CE Connection to VPLS

Virtual Private LAN Services
7750 SR OS Services Guide Page 353
Dual Homing to a VPLS Service
Figure 8: Dual Homed CE Connection to VPLS
Figure 40 illustrates a dual-homed connection to VPLS service (PE-A, PE-B, PE-C, PE-D) and
operation in case of link failure (between PE-C and L2-B). Upon detection of a link failure PE-C
will send MAC-Address-Withdraw messages, which will indicate to all LDP peers that they
should flush all MAC addresses learned from PE-C. This will lead that to a broadcasting of
packets addressing affected hosts and re-learning process in case alternative route exists.
Note that the message described here is different than the message described in draft-ietf-l2vpn-
vpls-ldp-xx.txt, Virtual Private LAN Services over MPLS. The difference is in the interpretation
and action performed in the receiving PE. According the draft definition, upon receipt of a MAC-
withdraw message, all MAC addresses, except the ones learned from the source PE, are flushed,
L2-A
PE-A
PE-B
L2-B
PE-C
PE-D
MAC flush
Link down
OSSG117
L2-A
PE-A
PE-B
L2-B
PE-C
PE-D
L2-A
PE-A
PE-B
L2-B
PE-C
PE-D
L2-A
PE-A
PE-B
L2-B
PE-C
PE-D