Cat4500-E Sup 6/7-E Etherchannel Egress Queueing

QoS on Cat4500-E with a Sup 6/7-E is more aligned to the Modular QoS CLI (MQC) known from router platforms then on a Cat6500, even though it still got restrictions based on the architecture compared to routers. The Cat4500-E switches perform all QoS actions on the supervisor engine, therefore the line cards do not add to the QoS complexity with their own queueing structure. The whole chassis uses an 1P7Q1T (1 Priority queue, 7 normal Queues, 1 Threshold) queueing structure. But there is a gotcha for QoS on Etherchannel (how surprising 😉 ), the QoS documentation shows the following restrictions:

  • Queuing actions are only allowed in the egress direction and only on the physical port.
  • Percentage-based actions like policer cannot be configured on a VLAN, Port and VLAN (PV) and EtherChannel.
  • Port channel or VLAN configuration can only have a policing or a marking action, not a queueing action.

The example configuration below shows what this means in terms of configuration. The priority queue has to be defined on the physical ports while the policing action is configured on the port-channel interface.

Example Configuration

class-map match-any PRIORITY-QUEUE
 match  dscp ef
 class class-default
  police cir 2g
int po 1
 service-policy output EGRESS-QUEUING-LOGICAL
int te1/1
 service-policy output EGRESS-QUEUING-PHYSICAL
int te1/2
 service-policy output EGRESS-QUEUING-PHYSICAL

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