The following figure shows an example of remote PE (PE3) behavior when there is an ethernet-segment failure.
The following steps list the behavior of the remote PE3 for unicast traffic:
PE3 forwards MAC DA = CE2 to PE2 when the MAC advertisement route came from PE2 and the set of Ethernet AD per-ES routes and Ethernet AD per-EVI routes from PE1 and PE2 are active at PE3.
If there is a failure between CE2 and PE2, PE2 withdraws its set of Ethernet AD and ES routes. PE3 does not need to wait for the withdrawal of the individual MAC, and immediately forwards the traffic destined for CE2 to PE1 (the backup PE) only.
After the (2) PE2 withdraws its MAC advertisement route, PE3 treats traffic to MAC DA = CE2 as unknown unicast, unless the MAC has been previously advertised by PE1.
A DF election on PE1 is also triggered. A DF election is triggered by the same events as all-active multi-homing. In this case, the DF forwards traffic to CE2 when the esi-activation-timer expires; the timer is triggered when a transition from non-DF to DF occurs.