Catalyst 9400 Hardware Queuing

[Alex Hwang]

Hi guys,

I have a question around Catalyst9400 hardware queuing.

We are planning to replace C3750X stacks with Catayst9404R switches. Currently 4Q3T model (without priority queue) is deployed on C3750X and we want to retain existing QoS configuration.

According to Catalyst9000 document, maximum of 8 queuing classes are supported on the device port for the wired target. Switch ports can be configured with an 8Q3T, 1P7Q3T, or 2P6Q3T egress queuing model.

My question is if we configure only 4 queue classes on C9404R for queuing, Do you expect any disadvantage in terms of performance?  e.g. The switch ports on C9400 only utilize half (4 of total 8 hardware queues) capacity.

Cheers

[Joseph W. Doherty]

Unsure about the C9400, but buffers might be "reserved", by default, for unused queues as they would on your 3750X (also by default with QoS enabled). If so, likely you can change buffer allocations.