Is it necessary to trust DSCP on switch trunk links?

[Paul Morgan]

Hi All,

Im really losing it with my QOS statistics. I am not seeing the DSCP markings I would expect passing through my switch interfaces and I dont know why.

Ive configured all ports connected to voip phones (non-Cisco) as below. Most have PCs connected too.

interface FastEthernet0/1
 switchport access vlan 177
 switchport mode access
 switchport voice vlan 169
 priority-queue out
 mls qos trust dscp
 spanning-tree portfast

Ive configured the trunks as below:

interface GigabitEthernet0/1
 switchport mode trunk
 switchport nonegotiate
 priority-queue out

Im not seeing the DSCP count for EF(46) going up in the outbound direction to the phones.

I can see the count inbound on the trunk counting up but nothing out to the phones.

Do I need to add the trust dscp command to the trunk or is there something I am missing?

The switch is a 2960 48 port with ios15.

Any help is much appreciated

[Joseph W. Doherty · Accepted solution]

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Posting

Yes, add trust on the trunk interface.

[Paul Morgan]

well what'd'ya'know... Simple as that

Thanks.