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Cisco Bug: CSCuq73517 - PBB-EVPN: single-active LB: backup PE not flushing during link recovery

Last Modified

May 11, 2018

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

5.1.2.BASE

Description (partial)

Symptom:
Longer than expected traffic outage (e.g. CAM age timeout timer) could be observed during recovery of access links in a PBB-EVPN dual-home device scenario using single-active load balance configuration

Conditions:
Assume the topology:
    PE1
    /
   /
CE1
  \
   \
    PE2
   /
  /
CE2

This outage is due to the fact that during recovery of the link to the primary PE (CE1-PE1 link), the backup PE (PE2) is not flushing the MACs previously learnt on its link to the dual-homed CE(CE1-PE2). During recovery of the before mentioned link, the Ethernet flow points on PE2 transition from forwarding to blocking and thus the flushing on PE2 is the expected behavior.

Worst case traffic outage scenarios occur with unidirectional traffic (CE2-CE1 direction) and when the dual-home CE (CE2) is not configured to react to incoming TCN from the primary PE (e.g. STP TCN or MVRP)
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