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Defining CoS Rewrite Rules

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.

Note:

OCX Series switches do not support MPLS, so they do not support EXP rewrite rules.

Note:

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.

Note:

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.

Note:

For packets that carry both an inner VLAN tag and an outer VLAN tag, the rewrite rule rewrites only the outer VLAN tag.

To create rewrite rules and enable them on interfaces:

  • To create an 802.1p rewrite rule named customup-rw in the rewrite table for all Layer 2 interfaces:

  • To enable an 802.1p rewrite rule named customup-rw on a Layer 2 interface:

    Note:

    All forwarding classes assigned to port xe-0/0/7 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.

  • To enable an 802.1p rewrite rule named customup-rw on all 10-Gigabit Ethernet interfaces on the switch, use wildcards for the interface name and logical interface (unit) number:

    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.