QoS 802.1p mapping on ingress port

[Zhang_Lu]

Hi all,

I would like to do a 802.1p marking on the ingress port on the switch, because the end node itself cannot mark 802.1p or DSCP value on its frame/packet.

How I can do this?

BR

Lu

[StephenW]

Zhang,

Yes you can. You can do this by using an Ingress ACL to add a dscp value based on the diffserv replacement mappings on the switch. In this example below a DSCP code point of 32 will be added on egress.

Note: When you add a new DSCP value on ingress it will not be examined on egress. But the next switch in line will be able to prioritize the traffic on egress.

1 Apply ACL to your ingress port:

entry replace_DSCP_32 {
if match all {
}
then {
qosprofile qp5 ;
replace-dscp ;
}
}

2. Change the diffserv replacement mappings

Switch# configure diffserv replacement qp5 code-point 32
Switch# show diffserv replacement
QOSProfile->CodePoint mapping:
QP1 -> 00
QP5 -> 32
QP8 -> 56

Hope this helps.

[StephenW]

Also, don't forget to enable diffserv replacement on the ingress port. 🙂

Switch# enable diffserv replacement ports

[Zhang_Lu]

Hi Williams,

Can we also change the DSCP value for a packet, if there is no L3 function enabled on the switch?

I mean, like a vlan which is not enabling ipforwarding, can we do a DSCP marking on the ingress untagged port for the traffic from that vlan?

Thanks

[StephenW]

Christoph,

Here is a example. Lets say your ingress port is 1:1 and you want to add a dot1p value of 4 to all the traffic coming into that port. This is what you would do.

1. Apply this ACL to port 1:1:

entry replace_dot1p_4{
if match all {
} then {
permit ;
replace-dot1p-value 4 ;

} }

Note: Dot1p is in the 802.1q part of the frame so 802.1q tagged frames will have the dot1p value. If port 1:1 is untagged it will not work.

Link to GTAC Knowledge Article on this topic