Rewriting IEEE 802.1p Packet Headers with an MPLS EXP Value
For Ethernet interfaces on Juniper Networks M320 Multiservice Edge Routers, MX Series Ethernet Service Routers, T Series Core Routers, and EX Series switches that have a peer connection to an M Series Multiservice Edge Router, MX Series router, T Series router, or EX Series switch, you can rewrite both MPLS EXP and IEEE 802.1p bits to a configured value. This enables you to pass the configured value to the Layer 2 VLAN path. For IQ PICs, you can only configure one IEEE 802.1 rewrite rule on a physical port. All logical ports (units) on that physical port should apply the same IEEE 802.1 rewrite rule.
To rewrite both the MPLS EXP and IEEE 802.1p bits,
you must include EXP and IEEE 802.1p rewrite rules in the interface
configuration. To configure EXP and IEEE 802.1p rewrite rules,
include the rewrite-rules statement at the [edit class-of-service
interfaces interface-name unit logical-unit-number] hierarchy level, specifying the exp and ieee-802.1 options:
[edit class-of-service interfaces interface-name unit logical-unit-number] rewrite-rules { exp rewrite-rule-name; ieee-802.1 default; }
When you combine these two rewrite rules, only the EXP rewrite table is used for rewriting packet headers. If you do not configure a VLAN on the interface, only the EXP rewriting is in effect. If you do not configure an LSP on the interface or if the MPLS EXP rewrite rule mapping is removed, the IEEE 802.1p default rewrite rules mapping takes effect.
You can also combine other rewrite rules. IP, DSCP, DSCP IPv6, and MPLS EXP are associated with Layer 3 packet headers, and IEEE 802.1p is associated with Layer 2 packet headers.
For IQ PICs, you can only configure one IEEE 802.1 rewrite rule on a physical port. All logical ports (units) on that physical port should apply the same IEEE 802.1 rewrite rule.
If you combine IEEE 802.1p with IP rewrite rules, the Layer 3 packets and Layer 2 headers are rewritten with the IP rewrite rule.
If you combine IEEE 802.1p with DSCP or DSCP IPv6 rewrite rules, three bits of the Layer 2 header and six bits of the Layer 3 packet header are rewritten with the DSCP or DSCP IPv6 rewrite rule.
For MPCs, default EXP rewrite rules do not exist for logical interfaces. The EXP CoS bits for MPLS labels are obtained from the IP precedence bits for IP traffic. The EXP bits for labels that are pushed or swapped are inherited from the current label of the MPLS packets. For non-IP and non-MPLS packets, the EXP bits are set to 0. If a custom EXP rewrite rule is configured on the core-facing interface, then it overrides the EXP bits.
The following example shows how to configure an EXP rewrite rule and apply it to both MPLS EXP and IEEE 802.1p bits:
[edit class-of-service]
rewrite-rules {
exp exp-ieee-table {
forwarding-class best-effort {
loss-priority low code-point 000;
loss-priority high code-point 001;
}
forwarding-class assured-forwarding {
loss-priority low code-point 010;
loss-priority high code-point 011;
}
forwarding-class expedited-forwarding {
loss-priority low code-point 111;
loss-priority high code-point 110;
}
forwarding-class network-control {
loss-priority low code-point 100;
loss-priority high code-point 101;
}
}
}
interfaces {
so-3/1/0 {
unit 0 {
rewrite-rules {
exp exp-ieee-table;
ieee-802.1 default;
}
}
}
}