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Cisco Bug: CSCvv37157 - ASR9K: L2MCAST traffic drops visible in the fabric-queue on Tomahawk LCs

Last Modified

Oct 01, 2020

Products (1)

  • Cisco ASR 9000 Series Aggregation Services Routers

Known Affected Releases

6.5.3.BASE 6.6.3.BASE

Description (partial)

Symptom:
Multicast traffic drops visible in the fabric-queue for priority normal:

RP/0/RSP0/CPU0:513E.G.53-ASR9006-1#show qoshal fabric-queue np 0 location 0/0/CPU0
[...]
    Ingress: QID 0x82 Entity: 0/0/0/4/8/2 Priority: Priority Normal Qdepth: 22
            StatIDs: commit/drop: 0x107292/0x868a08
            Statistics(Pkts/Bytes):
              Total Xmt 7206258655/10247284716722 Dropped 56/79632
[...]
    Ingress: QID 0x80082 Entity: 0/1/0/4/8/2 Priority: Priority Normal Qdepth: 22
            StatIDs: commit/drop: 0x187292/0xa68a08
            Statistics(Pkts/Bytes):
              Total Xmt 7206261691/10247288045190 Dropped 66/93852

RP/0/RSP0/CPU0:513E.G.53-ASR9006-1#show drops all location 0/0/CPU0 | inc TM
Sun May 23 04:54:00.332 UTC
[np:NP 0 TM 0] drop paks: 56
[np:NP 0 TM 1] drop paks: 66

Conditions:
Issue is seen on Tomahawk based LCs when all the following conditions are met:
[1] Multicast traffic or unknown-unicast(flood) traffic is ingressing on a L2 interface in a bridge-domain.
[2] Bridge-domain has BVI configured.
[3] The incoming L2 interface does not have any QoS policy applied in the ingress direction
[4] The BVI interface does not have any QoS policy applied in the ingress direction.
[5] There are one or more bridge-members (other than the BVI) where traffic needs to be multicasted/flooded.
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