On Thu, Jan 23, 2014 at 2:41 AM, Alexandre Snarskii <s...@snar.spb.ru> wrote: > On Wed, Jan 22, 2014 at 09:20:36AM -0700, John Neiberger wrote: >> I ran into an issue yesterday that confused me, which seems to be a >> weekly occurrence lately regarding Juniper CoS.. We had an interface >> that was receiving traffic marked as EF. The interface only had the >> default CoS configuration. For some reason, the traffic was arriving >> at the destination marked as CS0. After I applied the CoS group to the >> interface, which included classifiers, the packets started arriving at >> the destination as EF like they were supposed to be. >> >> I don't understand why a lack of CoS config would reset DSCP markings >> for traffic that is already marked when it hits the router. Could it >> be that since there were no ingress classifiers, the traffic was not >> put into a forwarding class, so the rewrite rules on egress re-marked >> it? > > When there are no explicit classifiers configured for interface, there > are implicit "default ones" applied: > > s...@lab.spb> show class-of-service interface ge-1/0/0.13 detail > Logical interface: ge-1/0/0.13, Index: 336 > Object Name Type Index > Classifier ipprec-compatibility ip 13 > > and yes, this classifier maps EF (DSCP 101110 = IPPREC 101) traffic > to BE forwarding class: > > s...@lab.spb> show class-of-service classifier name ipprec-compatibility > Classifier: ipprec-compatibility, Code point type: inet-precedence, Index: 13 > Code point Forwarding class Loss priority > 000 best-effort low > 001 best-effort high > 010 best-effort low > 011 best-effort high > 100 best-effort low > 101 best-effort high > 110 network-control low > 111 network-control high > > so rewrite-rule configured on outbound interface will rewrite dscp/ipprec > to all-zeros (default for BE).
Ah, that's exactly it. That explains the mystery. I'm pretty sure I get it now, but I thought that same thing last week. :) Thanks to everyone who helped me get this straightened out in my head. John _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp