Bug Report: Tagged VLAN traffic has PCP/CoS field set to 5

Question

Reference: https://en.wikipedia.org/wiki/IEEE_802.1Q. The PCP field is also known as priority / class-of-service.

This is happening on all tagged VLAN traffic, including ARP packets. I tried two switches: an ICX 6450 and an ICX 7250.

Using `ip pcp-remark 0` on the VE interface corrects all traffic except ARP.

This is a very strange behavior -- possibly a bug? Can someone else confirm this?

Chandini · Answer

Hi Orea

Understood. As per the below link ICX switches decide a packet’s priority by checking several things in order. First, they look for an ACL that sets a priority. If not found, they check if the packet’s MAC address matches a static entry with a set priority. If neither applies, they use the default priority of the incoming port, then check the DSCP/ToS value, followed by the 802.1p CoS value. If none of these are set, the packet gets a default priority of 0 as per the link below.

* https://docs.commscope.com/bundle/fastiron-08095-trafficguide/page/GUID-61D1CC9C-659F-4055-B8D8-38B396DF7EFC.html
* https://docs.commscope.com/bundle/fastiron-08095-trafficguide/page/GUID-404A417C-0402-49C4-B74A-10006B8656C5.html

I recommend opening a support case with us so we can assist you further. We'd be happy to work with you to verify the CoS value you're observing in the 802.1Q Ethernet frame header.

* https://support.ruckuswireless.com/contact-us

Thank you

oreo · Answer

No, I am talking about the 802.1Q frame of an Ethernet packet. With the above configuration, a packet within VLAN 210 going out of interface 1/1/1 has the priority field set to 5, which is unexpected.

Chandini · Answer

Hi Oreo

Ack and Thank you for reaching us

You mean Q5 in the interface output for port 1/1/1 ?

For Example : Q5 in the Egress Q ?

Thank you