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Cisco Bug: CSCut13789 - IPv6 multicast traffic not switched in bd on RPF failure

Last Modified

Feb 03, 2017

Products (1)

  • Cisco ASR 920 Series Aggregation Services Router

Known Affected Releases

15.5(1)S

Description (partial)

Symptom:
In a dual-homing environment, on which VRRP is being run for Node level Redundancy . IP routed multicast elects a DR and a BDR from the 2 920's in the topology.
920 (DR) ---------------920(BDR)
  |                                |
   --------ME1200-----

With the direct link to the DR not available from the receiver ,the receiver send the joins to the DR via the BDR since direct route is not available. The BDR forwards the joins on the links towards the DR and the uplink towards the intended source. The DR receives the traffic from the uplink and forwards it to the BDR. The BDR has the routes from 2 sources now,with the route from DR shorter, due to which RFC  blocks the traffic .

Conditions:
The dual homing scenario has VRRP running to provide node redundancy between 2 ASR920's. Also G8032 is running as an ethernet ring protection service for the ring
The DR is the master of the VRRP group and the BDR is the backup for the VRRP group.
The RPL link is between the ASR920's

Scenario : The ring is broken thus leading to the direct link between the ASR920's to get unblocked as an expected behavior for the G8032 feature. Due to this the receiver attached to L2 switch sends the joins via bdr to dr .
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