Defining CoS Rewrite Rules
Overview
Edge switches might need to change the class-of-service (CoS) settings of the packets. You can configure rewrite rules to alter code point bit values in outgoing packets on the outbound interfaces of a switch so that the CoS treatment matches the policies of a targeted peer. Policy matching allows the downstream routing platform or switch in a neighboring network to classify each packet into the appropriate service group.
To configure a CoS rewrite rule, create the rule by giving it a name and associating
it with a forwarding class, loss priority, and code point. This creates a rewrite
table. After the rewrite rule is created, enable it on an interface (EXP rewrite
rules can only be enabled on family mpls logical interfaces, not on
physical interfaces). You can also apply an existing rewrite rule on an
interface.
On each physical interface, either all forwarding classes that are being used on the interface must have rewrite rules configured, or no forwarding classes that are being used on the interface can have rewrite rules configured. On any physical port, do not mix forwarding classes with rewrite rules and forwarding classes without rewrite rules.
To replace an existing rewrite rule on the interface with a new rewrite rule of the same type, first explicitly remove the existing rewrite rule and then apply the new rule.
For packets that carry both an inner VLAN tag and an outer VLAN tag, the rewrite rule rewrites only the outer VLAN tag.
Platform-specific Information
-
OCX Series switches do not support MPLS, so they do not support EXP rewrite rules.
-
QFX5130, QFX5700 & QFX5220 switches do not support DSCP IPv6 classifiers and rewrite rules. However, you can apply DSCP classifiers and rewrite rules for IPV6 traffic as well.
Configuring Rewrite Rules
To create rewrite rules and enable them on interfaces:
To create an 802.1p rewrite rule named
customup-rwin the rewrite table for all Layer 2 interfaces:[edit class-of-service rewrite-rules] user@switch# set ieee-802.1 customup-rw forwarding-class be loss-priority low code-point 000 user@switch# set ieee-802.1 customup-rw forwarding-class be loss-priority high code-point 001 user@switch# set ieee-802.1 customup-rw forwarding-class be loss-priority low code-point 010 user@switch# set ieee-802.1 customup-rw forwarding-class fcoe loss-priority low code-point 011 user@switch# set ieee-802.1 customup-rw forwarding-class ef-no-loss loss-priority low code-point 100 user@switch# set ieee-802.1 customup-rw forwarding-class ef-no-loss loss-priority high code-point 101 user@switch# set ieee-802.1 customup-rw forwarding-class nc loss-priority low code-point 110 user@switch# set ieee-802.1 customup-rw forwarding-class nc loss-priority high code-point 111
To enable an 802.1p rewrite rule named
customup-rwon a Layer 2 interface:[edit] user@switch# set class-of-service interfaces xe-0/0/7 unit 0 rewrite-rules ieee-802.1 customup-rw
Note:All forwarding classes assigned to port
xe-0/0/7must have rewrite rules. Do not mix forwarding classes that have rewrite rules with forwarding classes that do not have rewrite rules on the same physical interface.To enable an 802.1p rewrite rule named
customup-rwon all 10-Gigabit Ethernet interfaces on the switch, use wildcards for the interface name and logical interface (unit) number:[edit] user@switch# set class-of-service interfaces xe-* unit * rewrite-rules customup-rw
Note:In this case, all forwarding classes assigned to all 10-Gigabit Ethernet ports must have rewrite rules. Do not mix forwarding classes that have rewrite rules with forwarding classes that do not have rewrite rules on the same physical interface.