Symptom

An ASR 9000 Tomahawk or Typhoon linecard experiences poor fabric forwarding performance and FIA tail drops for ingress MPLS packets. FIA classifies the packets as priority 3, when ingress policy sets EXP bit.

Conditions

This may occur when an MQC service-policy with

set mpls experimental topmost

action is applied in the ingress direction on the Tomahawk LC. Issue is applicable to Tomahawk/Typhoon LC (ingress)

Workaround

It may be possible to achieve the desired mpls marking behavior without ingress exp topmost marking, by using ingress exp imposition marking, ingress qos-group marking, and/or egress exp topmost marking. These actions will not trigger the bug.

Further Problem Description