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Cisco Bug: CSCur72468 - L3 mcast packet should be dropped if OLE entry in HW is invalid

Last Modified

Sep 17, 2019

Products (7)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9922 Router
  • Cisco ASR 9010 Router
  • Cisco ASR 9904 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9912 Router

Known Affected Releases

5.3.0.BASE 5.3.1.BASE

Description (partial)

Symptom:
Duplicate or unexpected L3 multicast packets seen at receiver when L3 multicast route has invalid/incorrect OLE. (OLE = Output List Element which is a hardware instance of a multicast outgoing interface associated with a multicast route)

Conditions:
When a L3 multicast route has an invalid OLE entry in HW, instead of dropping the packet dataplane create a copy of the packet and punts it to LC CPU. If the packet were to get re-injected back to the NP this causes unpredictable behavior. One of the behaviors seen was that this extra packet was eventually forwarded out. If the L3 multicast route already had valid OLE entries apart from the invalid ones we would see the packets from the valid OLE entries plus the punted/re-injected packets hence showing up as duplicate packets at the receiver

The following NP counters with matching pps are seen on the egress NP when the situation happens:

RSV_PUNT_IP_MTU_EXCEEDED
IPV4_FRAG_NEEDED_PUNT
MDF_TX_LC_CPU                                          

This issue was seen when a BVI interface was one of the OLEs associated with the L3 mcast route
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