(It has been done on more interfaces, but they are all the same as this Gi2/2.)
Now, this is the entire configuration of this interface:
switchport access vlan 11
switchport mode access
service-policy output autoqos-voip-policy
qos trust cos
auto qos voip trust
shape percent 33
For completeness, here's the CoS to DSCP map:
CoS-DSCP Mapping Table
CoS: 0 1 2 3 4 5 6 7
DSCP: 0 8 16 26 32 46 48 56
And the DSCP to tx-queue map:
DSCP-TxQueue Mapping Table (dscp = d1d2)
d1 : d2 0 1 2 3 4 5 6 7 8 9
0 : 01 01 01 01 01 01 01 01 01 01
1 : 01 01 01 01 01 01 02 02 02 02
2 : 02 02 02 02 04 04 04 04 04 04
3 : 04 04 04 04 04 04 04 04 04 04
4 : 03 03 03 03 03 03 03 03 04 04
5 : 04 04 04 04 04 04 04 04 04 04
6 : 04 04 04 04
The only DSCP relevant to tx-queue 3 (which we are prioritising) that has an entry in the CoS-to-DSCP map is DSCP 46, being CoS 5.
Since all ports are configured as "qos trust cos", they are trusting the CoS values of frames on ingress. I hope I am still interpreting this correctly when I conclude that this means that frames that have CoS set to 5 on ingress will be prioritised on egress.
Now, onto my "real" question; our QoS here is based on CoS, which is a classification on layer 2, more specificly the CoS is defined in the User field of layer 2 frame with trunk encapsulation. So for my switch to actually find a CoS value the received frame has to tagged either as 802.1Q or ISL. But my switchports aren't trunks, they are access ports.
Does this mean that QoS isn't working or is it possible to receive trunk frames on an access port and the switch will know how to deal with this?
While this may sound strange, it is possible to receive tagged frames on access ports. You can enable this by using the Voice VLAN feature. You can configure the port so that an attached IP phone sends voice frames tagged with the Voice VLAN ID and also sends data from any attached PC as untagged frames. That is a scenario in which the 'qos trust cos' may come in useful.
Here's a link to more info on configuring voice vlans:
Thank you for clarifying that it is possible to receive tagged frames on access ports. That helps.
I do not have Voice VLAN activated on any of my ports though, am I correct in assuming that activing the Voice VLAN feature is not required for me to be able to receive tagged frames on that access port?
We are actually using some third party software (Vocalcom) of which I do not (yet) have any specs. It is entirely possible that this is functioning similar to the Cisco IP phones though, sending data without a tag and voice tagged and classified as CoS 5.
If you have not activated that voice vlan feature, that means that your switch will expect to see only untagged frames on that port. In such a case, 'qos trust cos' really has no meaning, since there is no CoS field without an ISL/802.1q tag.
If this application of yours is sending tagged traffic, you will need to configure a voice vlan on the port so that the switch knows what to do with the tagged traffic...
"When the interface trust state is not configured to trust dscp using the qos trust dscp command, the security and QoS ACL classification will always use the interface DSCP and not the incoming packet DSCP. "
Regarding my understanding you must have an 801.Q trunk, for handling CoS in a port, because the field CoS only is present over this encapsulation method. In fact, if you review the Ethernet encapsulation there is not any Cos field, that means that you need a trunk always for handle CoS over a trunk.
The short answer is that you don't.... That isn't entirely true while at
the same time it kind of is, but for the most part you don't configure
the softkeys. You enable or disable them via TCL. Here is the long
answer. Be sure to read the whole thing or e...
Topology: IP Phone > Switches > Microsoft NPS setup to forward 802.1x
proxy to > ISE 2.1 patch 3 Authentication: EAP-TLS using Cisco MIC SANs
Phone Models 802.1X support? 802.1x flavor Addtl Comment EAP-MD5 EAP-TLS
Cisco 3905 Y Y N Cisco 6911 Y Y N Cisco ...
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