O'Reilly logo

MPLS Fundamentals by Luc De Ghein - CCIE No. 1897

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Default MPLS QoS Behavior in Cisco IOS

In Cisco IOS, the default behavior when imposing one or more labels on an IP packet is to copy the precedence value to the EXP bits of all imposed labels. This is called TOS reflection, because nothing regarding QoS changes by default. If, however, the six bits of the DSCP field are used, only the first three bits of DSCP are copied to the EXP bits of the labels. This leads to the first MPLS QoS rule.

MPLS QoS Rule 1

By default, in Cisco IOS, the precedence bits or the first three bits of the DSCP field in the IP header are copied to the EXP bits of all imposed labels at the ingress LSR.

Forwarding a labeled packet is a bit more complicated. You have to distinguish two cases: swapping a label, and possibly ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required