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). > That just occurred to me. I'm going to go check the rewrites rules > we have applied on egress to see if that is what was happening. I was > under the bad assumption that traffic already marked would traverse > the router unchanged. > > Thanks, > John > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/juniper-nsp -- In theory, there is no difference between theory and practice. But, in practice, there is. _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp