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Configuring Rewrite Rules

You define markers in the rewrite rules section of the CoS configuration hierarchy and reference them in the logical interface configuration. This model supports marking on the DSCP, DSCP IPv6, IP precedence, IEEE 802.1, and MPLS EXP CoS values.

To configure a rewrite-rules mapping and associate it with the appropriate forwarding class and code-point alias or bit set, include the rewrite-rules statement at the [edit class-of-service] hierarchy level:



[edit class-of-service]

rewrite-rules {


(dscp | dscp-ipv6 | exp | ieee-802.1 | inet-precedence) rewrite-name {

import (rewrite-name | default);



forwarding-class class-name {

loss-priority level code-point (alias | bits);
}


}


}

The rewrite rule sets the code-point aliases and bit patterns for a specific forwarding class and PLP. The inputs for the map are the forwarding class and the PLP. The output of the map is the code-point alias or bit pattern. For more information about how CoS maps work, see Table 7.

By default, IP precedence rewrite rules alter the first three bits on the type-of-service (ToS) byte while leaving the last three bits unchanged. This default behavior is not configurable. The default behavior applies to rules you configure by including the inet-precedence statement at the [edit class-of-service rewrite-rules] hierarchy level. The default behavior also applies to rewrite rules you configure for MPLS packets with IPv4 payloads. You configure these types of rewrite rules by including the mpls-inet-both or mpls-inet-both-non-vpn option at the [edit class-of-service interfaces interface-name unit logical-unit-number rewrite-rules exp rewrite-rule-name protocol] hierarchy level.

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