The packet marking feature provides users with a means to differentiate packets based on the designated markings. The router
supports egress packet marking. match on discard-class on egress, if configured, can be used for a marking policy only.
The router also supports L2 ingress marking.
For ingress marking:
Ingress traffic— For the ingress pop operation, re-marking the customer VLAN tag (CoS, DEI) is not supported.
Egress traffic— The ingress ‘pop VLAN’ is translated to a ‘push VLAN’ for the egress traffic, and (CoS, DEI) marking is supported
for newly pushed VLAN tags. If two VLAN tags are pushed to the packet header at the egress side, both inner and outer VLAN
tags are marked. For example:
1. rewrite ingress tag pop 1 symmetric
2. rewrite ingress tag pop 2 symmetric
3. rewrite ingress tag translate 2-to-1 dot1q/dot1ad <> symmetric
Limitation
The statistics and counters for the egress marking policy cannot be viewed on the router.
Supported
Packet Marking Operations
This table shows the supported packet marking operations.
Supported Mark Types
|
Range
|
Support
for Unconditional Marking
|
Support
for Conditional Marking
|
set cos
|
0-7
|
ingress
|
No
|
set dei
|
0-1
|
ingress
|
No
|
set discard-class
|
0-3
|
ingress
|
No
|
set dscp
|
0-63
|
ingress
|
No
|
set mpls experimental topmost
|
0-7
|
ingress
|
No
|
set precedence
|
0-7
|
ingress
|
No
|
set
qos-group
|
0-7
|
ingress
|
No
|
Class-based
Unconditional Packet Marking
The packet marking feature allows you to partition your network
into multiple priority levels or classes of service, as follows:
-
Use QoS unconditional
packet marking to set the IP precedence or IP DSCP values for packets entering
the network. Routers within your network can then use the newly marked IP
precedence values to determine how the traffic should be treated.
On ingress direction, after
matching the traffic based on either the IP Precedence or DSCP value, you can
set it to a particular discard-class. Weighted random early detection (WRED), a
congestion avoidance technique, thereby uses discard-class values to determine
the probability that a packet is dropped.
-
Use QoS unconditional packet marking to assign MPLS packets to a QoS group. The router uses the QoS group to determine how
to prioritize packets for transmission. To set the QoS group
identifier on MPLS packets, use the set qos-group
command in policy map class configuration mode.
![](https://www.cisco.com/content/dam/en/us/td/i/templates/note.gif) Note |
Setting the QoS group identifier does not automatically prioritize the packets for transmission. You must first configure
an egress policy that uses the QoS group.
|
-
Use QoS unconditional packet marking to assign packets to set the priority value of IEEE 802.1p/
Inter-Switch Link (ISL) packets.
The router uses the CoS value to determine how to prioritize packets for transmission and can use this marking to perform
Layer 2-to-Layer 3 mapping. To set the Layer 2 CoS value of an outgoing packet, use the set cos command in policy map configuration mode.
-
Use QOS unconditional packet marking to mark a packet based on the drop eligible indicator value (DEI) bit on 802.1ad frames.
To set the DEI value, use the set dei command to set the drop eligible indicator value (DEI) in policy map class configuration mode.
![](https://www.cisco.com/content/dam/en/us/td/i/templates/note.gif) Note |
-
Conditional packet marking is not supported.
-
Unless
otherwise indicated, the class-based unconditional packet marking for Layer 3
physical interfaces applies to bundle interfaces.
|