[c-nsp] 7600s, DSCP, ASICs, Bollocks

James Bensley jwbensley at gmail.com
Tue Nov 17 12:41:51 EST 2015


All fixed;

To recap:
Traffic comes in via transit provider attached to 7600-PE1, label is
pushed, traffic is label switched over to 7600-PE2, PE2 PoPs label and
sends IP traffic to customer.

Packets are coming from the transit provider with a DSCP making and
being sent over to the customer with a DSCP marking. I'm was trying to
set the incoming packets to DSCP 0 on PE1 first, with a policy-map
with "set DSCP 0" which didn't work. Then without a policy map the
port is by default in a state of un-trust as mls qos is enabled
gobally. Still this didn't work.

By default the 7600/PFC is operating in short pipe mode:
http://www.cisco.com/c/en/us/td/docs/routers/7600/ios/15S/configuration/guide/7600_15_0s_book/mplsqos.html#pgfId-1405948

Switching to uniform mode work, using the global config command "mls
mpls qos input uniform-mode".

Now PE1 will set DSCP 0 on the incoming transit packets however, even
in short pipe mode, if the port is untrusted I would have expected the
DSCP to be set to 0. It seems in short pipe mode no actions can be
made against the DSCP/ToS value at ingress only egress.

Cheers,
James.


More information about the cisco-nsp mailing list