Multiple QoS on a L2 interface

[Gentry]

Hi,

We have a stack 2960 and all phones are Cisco 9951/9971. I'm looking at the config and all these commands are in an interface. Is it an overkill to have mls qos trust device cisco-phone, mls qos trust cos, and auto qos voip cisco-phone command on the same interface? Do I need all these commands? If not, which one do you recommend keeping or removing? Thanks

interface GigabitEthernet1/0/1
switchport access vlan 100
switchport mode access
switchport voice vlan 200
srr-queue bandwidth share 10 10 60 20
queue-set 2
priority-queue out
mls qos trust device cisco-phone
mls qos trust cos
auto qos voip cisco-phone
spanning-tree portfast
service-policy input AutoQoS-Police-CiscoPhone

[R0g22]

Since you have auto QoS, most of the qos config will be auto generated by the switch. Talking about the trust commands, the default switch behaviour is not to trust any ingress flow. You basically can set a trust boundary based on DSCP, COS or IP Phone. If you have a cisco ip phone, trust device is recommended along with trust dscp or trust cos.

Read more around CoS/ToS and DSCP PHB to get a hand of what and why they are used.

[Gentry]

Thanks, Nipun. So having mls qos trust device cisco-phone and mls qos trust cos commands are necessary when I'm using Cisco phones but do I still need the auto qos voip cisco-phone command on that same interface. The reason is that some of the interfaces didn't have that command, a little confusing.

interface GigabitEthernet1/0/4
switchport access vlan 100
switchport mode access
switchport voice vlan 200
mls qos trust device cisco-phone
mls qos trust cos
spanning-tree portfast

[R0g22]

Auto QoS is basically a macro that once enabled on a port applies recommended config for VoIP/IP Phone to the port and enables QoS globally if not already done. Your ports that don't have it, would mean that the QoS configuration was added manually. Another difference that you would see is that the non-auto qos ports don't have a service policy.

[Gentry]

Thanks, Nipun. I understand that interfaces that don't have a service-policy configured don't have auto qos voip cisco-phone assign. My questions are:
1. Do I need the auto qos voip cisco-phone command?
2. Why some ports have it and some not? If we're all using Cisco phones.
3. Is it safe/recommended to have the auto qos voip cisco-phone command along with mls qos trust device cisco-phone and mls qos trust cos or should I remove it completely?

Thanks again.

[R0g22]

Read my post again please. The reason you have all the commands related to QoS is because of Auto-QoS. Why some ports have it and some don't ? You need to talk to the person who maintains and configures your switches as to why he configured them on some while not on others.
Regarding the recommendation, if you are not really sure what you are doing and what you really need regarding QoS, it is relatively safe to just configure auto-qos and let the IOS generate the best configuration for you.