topic Re: Bug Report: Tagged VLAN traffic has PCP/CoS field set to 5 in ICX Switches

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

oreo — Sat, 31 May 2025 12:43:03 GMT

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?

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

Chandini — Sat, 31 May 2025 14:22:48 GMT

Hi Oreo

Thank you for reaching us.

Could you please share a screenshot or image for reference to help us better understand the specific details you're referring to?

Also, could you confirm the software version currently running on the switch?

Thank you

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

oreo — Sun, 01 Jun 2025 05:52:42 GMT

My issue is that the switches set the PCP/CoF/priority value to 5 when sending packets out a vlan tagged interface.

Example config:

!
vlan 210 by port
tagged ethe 1/1/1
router-interface ve 210
spanning-tree
!
interface ve 210
ip address 192.168.210.1 255.255.255.0
!

All packets going out of interface 1/1/1 will have PCP=5 in the 802.1Q frame. My expectation is that no priority value would be set since I have not configured QoS on the switch.

On the ICX 6450, I am running 08.0.30u. This is the latest available firmware. On the ICX 7250, I was running 08095m but I installed the latest available version (08.0.95r) and the behavior is still there.

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

oreo — Sun, 01 Jun 2025 17:53:36 GMT

My issue is that the switches set the PCP/CoF/priority value to 5 when sending packets out a vlan tagged interface.

Example config:

!
vlan 210 by port
tagged ethe 1/1/1
router-interface ve 210
spanning-tree
!
interface ve 210
ip address 192.168.210.1 255.255.255.0
!

All packets going out of interface 1/1/1 will have PCP=5 in the 802.1Q frame. My expectation is that no priority value would be set since I have not configured QoS on the switch.

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

Chandini — Tue, 03 Jun 2025 16:44:19 GMT

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

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

oreo — Tue, 03 Jun 2025 16:51:00 GMT

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.

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

Chandini — Thu, 05 Jun 2025 13:34:25 GMT

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.

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