Vlan 0 and priority tagging support

[JAN DEVOS]

Hello support community, 

In our OT environment there are devices setting 802.1p priority (COS) while using vlan tag 0 in their dot1q header.

1) on which switching platforms does Cisco support this feature? 
Reading  //www.cisco.com/c/en/us/td/docs/switches/connectedgrid/cg-switch-sw-master/software/configuration/guide/vlan0/b_vlan_0.html
this would be limited to IE2K, IE4K and IE5K, not IE3K nor Cat9K or any other switching device.  We are especially interested in IE3300

2) how to configure it?  The above configuration guide gives an example where the interface is configured as access port in VLAN 1 +  the 'encapsulation priority-tagged' statement.

This shall result in that the switch accepts ingress dot1q frames with vlanid 0, and honors their dot1p COS bits. May I suppose this configuration also results in preservation of vlan id = 0 and sender's COS bits when the frame leaves the egress port to its destination (as far as the ingress port is set to trust COS of course) ?  This would apply adequate queueing on egress among the packets in vlanid 0 (e.g. Cos 4 would take precedence over Cos 0).  Also this should prevent forwarding on this egress port of any untagged packet not part of the native vlan (so, better to use set the access port vlan to something else than 1, but a vlan-id that is certainly not used).

Is this above understanding correct?

[Georg Pauwen]

Hello,

I think you are correct. That is how I understand it as well:

--> Vlan ID 0 and CoS values/802.1P priority bits are preserved

--> no other untagged traffic other than the native Vlan traffic is forwarded. This of course is always the case, as there is no other untagged traffic than the native Vlan traffic.

[JAN DEVOS]

Thank you Georg, nice to read that my understanding is correct.  However, is there someone in the audience to answer Q1 above? Is dot1p priority setting + tagging in VLAN 0 supported on more switches than IE2K/4K/5K?  Especially IE3K is of interest for us.

[francisizquierdo]

Did you found any information about if the IE3300 support this feature?