priority-queue out command

[tedauction]

Hello, can you put the command 'priority-queue out' command on a trunk interface or is this only for layer 3 interfaces ?

Thank you.

[Mark Malone]

Hi

You would only use that on an access port layer 2 where a phone/pc is connected not on a trunk or layer 3 interface

it basically services the priority queue in qos before any other queue , be careful using this it can cause starvation for the other queues in mls qos when in place , you get 4 queues 1 p and 3 srr or wrr , the p queue when there's packets in it will be used first to ensure no delay in critical traffic like voice

[tedauction]

Hello guys, thanks for your replies however they seem contradictory.

Can someone please clarify if it is valid/common to use this command on a L2 trunk interface ?

My consideration is that if the trunk between two switches is bottlenecking, then perhaps this command would expedite EF marked traffic via 'priority-queue out'.

Thank you kindly.

[Joseph W. Doherty]

Unable to comment how "common" this is, especially as QoS isn't as common as it probably should be.

However, here's an interface config from an active 3560:

xxx#sh run in g0/1
Building configuration...

Current configuration : 247 bytes
!
interface GigabitEthernet0/1
 description PHY|1G|TRUNK|rhost:xxx|rport:ge0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
 srr-queue bandwidth share 25 5 25 70
 priority-queue out
 mls qos trust dscp
end

PQ is enabled to support DSCP EF.

[Joseph W. Doherty]

It should support any interface, trunk, L3 or L2.