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Cisco Bug: CSCul11074 - L2mcast cluster traffic drops at LR when IRL OLE switch to different LC

Last Modified

May 12, 2018

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

4.3.4.BASE

Description (partial)

Symptom:
ASR9k is a cluster. Inter Rack Links (IRL) are connected in different LCs between two racks.
IGMP snooping (L2 Multicast) traffic has receivers on both racks. IGMP snooping group selects
one of IRL links to forward traffic to receivers on remote rack. When the selected IRL link switches
from local LC to another LC, for example, the current IRL link is physically down or 
control plane reselects a new IRL link due to traffic load balance, traffic drops on 
the receiver of LC hosting the old IRL link.

Conditions:
1) ASR9k is a cluster. Inter Rack Links (IRL) are cross different LCs. 2) IGMPSN is enabled on the Bridge domain, where L2mcast traffic flows from Local Rack to egress receivers at the Remote Rack.
3) the LC currently hosting IRL link (OLE) has local receiver (LRs) of the l2mcat traffic.
4)  After the same group reselects a new IRL link from a different LC, the traffic could drop on the local receiver of the LC hosting the old IRL link.
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Bug Details Include

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