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Configuring DSCP Values for IPv6 Packets Entering the MPLS Tunnel

 

The following configuration example explains in detail how to set the DSCP and MPLS EXP bits independently on IPv6 packets.

1. Configure the router device (ingress PE router) to classify (behavior aggregate or multifield) the incoming packets to a particular forwarding class.

In the preceding example, the ingress FPC classifies (MF) incoming IPv6 packets destined for address “::ffff:192.0.2.128/120” to forwarding class “ss-fc” and loss priority “low.”

2. Attach the preceding firewall filter to an interface. Because you are matching on inbound traffic, this would be an input filter. This classifies all traffic on the interface “ge-2/1/0” that matches the filter “ss-v6.”

3. Configure the DSCP–IPv6 rewrite rule for the forwarding class “ss-fc.” This causes the outgoing IPv6 packets belonging to the forwarding class “ss-fc” and loss priority “low” to have their DSCP value rewritten to 100000.

4. Configure the EXP rewrite values for the forwarding class “ss-fc.” This rewrite rule stamps an EXP value of 100 on all outgoing MPLS packets assigned to the forwarding class “ss-fc” and loss priority “low.”

5. Apply the preceding rewrite rule to an egress interface. On the egress FPC, all IPv6 packets in the forwarding class “ss-fc” with loss priority “low” are marked with the DSCP value “100000” and an EXP value of “100” before they enter the MPLS tunnel.

6. To support IPv4 DSCP and MPLS EXP independent rewrite at the same time, you can define and apply an IPv4 DSCP rewrite rule “ss-dscp” to the same interface.