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Ask the Expert- SD-WAN

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Beginner

Qos commands difference

what is the different btw these 2 commands?

SUMMARY STEPS

  1. configureterminal
  2. interfaceinterface-id
  3. Use one of the following:
  • auto qos voip trust
  • auto qos trust{ cos | dscp}

in what situation do we use each of them??

 

1 ACCEPTED SOLUTION

Accepted Solutions
VIP Collaborator

Re: Qos commands difference

This is just my take.

 

The "auto qos voip trust" command trusts the voip markings on the interface and from what I see should be applied to uplink trunk ports to other switches or routers. The "auto qos trust cos|dscp" should be applied to trusted access ports. The following link is what I am basing this on:

 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/qos/configuration_guide/b_qos_152ex_2960-x_cg/b_qos_152ex_2960-x_cg_chapter_011.html

 

That being said, I really don't think there is a huge difference between the two. I tested this out on a 2960 and when I applied the "auto qos voip trust" command I got the following result:

!
interface GigabitEthernet1/0/11
 switchport access vlan 200
 switchport mode access
 switchport voice vlan 623
 load-interval 30
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
 spanning-tree portfast

If you apply the "auto qos trust cos" command you get the exact same result.

 

With the "auto qos trust dscp"

!
interface GigabitEthernet1/0/10
 switchport access vlan 200
 switchport mode access
 switchport voice vlan 623
 load-interval 30
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust dscp
 auto qos trust dscp
 spanning-tree portfast

 

In all cases the same priority and srr-queueing is enabled. The subtle difference is which markings are being used to apply the policy. I wouldn't recommend applying anything that is looking for COS markings on a non trunking port. Applying the trust DSCP on either access or trunking ports should always work.

Once again, my take, and maybe a bit wordy, but I hope this helps.

 

 

 

4 REPLIES 4
VIP Advisor

Re: Qos commands difference

Hi,

AutoQoS supports marked traffic with the auto qos voip trust interface configuration command. When you enter the auto qos voip trust interface configuration command, the autoQoS feature does the following:

If QoS was not already enabled, enables QoS globally.

If VLAN-based QoS was configured for the port, reverts to the default port-based QoS (done for all ports on switching modules with 1p1q0t/1p3q1t ports).

If the port is configured with the switchport command, sets the port trust state to trust CoS.

If the port is not configured with the switchport command, sets the port trust state to trust DSCP.

Basically auto qos voip trust is configured under interfaces connecting to routers or other switches so the classification will be considered as trusted and it is considered for ingress traffic only.

 

Please check this link under the section Auto Qos Trust

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/qos/command_reference/b_qos_152ex_2960-x_cr/b_qos_152ex_2960-x_cr_chapter_010.html#wp3145726977

 

Hope it is useful

:-)

Highlighted
Beginner

Re: Qos commands difference

i see u just quote the theory on the "auto qos voip trust" command.

i still do not see the difference and in which situation when to use either of them.

 

auto qos voip trust Vs auto qos trust dscp

VIP Collaborator

Re: Qos commands difference

This is just my take.

 

The "auto qos voip trust" command trusts the voip markings on the interface and from what I see should be applied to uplink trunk ports to other switches or routers. The "auto qos trust cos|dscp" should be applied to trusted access ports. The following link is what I am basing this on:

 

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/qos/configuration_guide/b_qos_152ex_2960-x_cg/b_qos_152ex_2960-x_cg_chapter_011.html

 

That being said, I really don't think there is a huge difference between the two. I tested this out on a 2960 and when I applied the "auto qos voip trust" command I got the following result:

!
interface GigabitEthernet1/0/11
 switchport access vlan 200
 switchport mode access
 switchport voice vlan 623
 load-interval 30
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust cos
 auto qos trust
 spanning-tree portfast

If you apply the "auto qos trust cos" command you get the exact same result.

 

With the "auto qos trust dscp"

!
interface GigabitEthernet1/0/10
 switchport access vlan 200
 switchport mode access
 switchport voice vlan 623
 load-interval 30
 srr-queue bandwidth share 1 30 35 5
 priority-queue out
 mls qos trust dscp
 auto qos trust dscp
 spanning-tree portfast

 

In all cases the same priority and srr-queueing is enabled. The subtle difference is which markings are being used to apply the policy. I wouldn't recommend applying anything that is looking for COS markings on a non trunking port. Applying the trust DSCP on either access or trunking ports should always work.

Once again, my take, and maybe a bit wordy, but I hope this helps.

 

 

 

VIP Expert

Re: Qos commands difference

"auto QoS" commands, I believe, can generate different configuration statements based on platform and/or IOS version. If I'm correct in my belief, I cannot define how all the commands will differ without knowing exactly what they will generate.

That noted, the VoIP trust probably builds policies to support a VoIP phone. The trust CoS or DSCP, would likely build policies to a least accept frames tagged with CoS, for the former, or packets with ToS (using DSCP), for the latter. Where the two are most likely to differ is what special treatment, if any, the policies provide to traffic that is believed to belong to VoIP.

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