Configuring Rewrite Rules for MPLS EXP Classifiers

date_range 24-Nov-23

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You configure EXP rewrite rules to alter CoS values in outgoing MPLS packets on the outbound family mpls interfaces of a switch to match 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 an EXP 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 a logical family mpls interface. EXP rewrite rules can only be enabled on logical family mpls interfaces, not on physical interfaces or on interfaces of other family types. You can also apply an existing EXP rewrite rule on a logical interface.

Note:

There are no default rewrite rules.

You can configure up to 64 EXP rewrite rules, but you can only use 16 EXP rewrite rules at any time on the switch. On a given family mpls logical interface, all pushed MPLS labels have the same EXP rewrite rule applied to them. You can apply different EXP rewrite rules to different logical interfaces on the same physical interface.

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.

To create an EXP rewrite rule for MPLS traffic and enable it on a logical interface:

Create an EXP rewrite rule:

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user@switch# set class-of-service rewrite-rules exp rewrite-rule-name forwarding-class forwarding-class-name loss-priority level code-points [aliases] [bit-patterns]

For example, to configure an EXP rewrite rule named exp-rr-1 for a forwarding class named mpls-1 with a loss priority of low that rewrites the EXP code point value to 001:

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user@switch# set class-of-service rewrite-rules exp exp-rr-1 forwarding-class mpls-1 loss-priority low code-points 001

Apply the rewrite rule to a logical interface:
```
user@switch # set class-of-service interfaces interface-name unit logical-unit rewrite-rules exp rewrite-rule-name
```
For example, to apply a rewrite rule named exp-rr-1 to logical interface xe-0/0/10.0:
```
user@switch# set class-of-service interfaces xe-0/0/10 unit 0 rewrite-rules exp exp-rr-1
```
Note:
In this example, all forwarding classes assigned to port xe-0/0/10 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 interface.

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Traffic Management User Guide (QFX Series Switches and EX4600 Switches)

Configuring Rewrite Rules for MPLS EXP Classifiers