Cisco 7604

41-59
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 41 Configuring PFC QoS
Configuring PFC QoS
Configuring DSCP Transparency
Note • In addition to support for other IP traffic, PFC3C and PFC3CXL mode support the no mls qos
rewrite ip dscp command for these traffic types:
– MPLS traffic
– Traffic in IP in IP tunnels
– Traffic in GRE tunnels
• In addition to support for other IP traffic, PFC3B and PFC3BXL mode support the no mls qos
rewrite ip dscp command for these traffic types:
– Except on PE routers, MPLS traffic
– Traffic in IP in IP tunnels
– Traffic in GRE tunnels
• PFC3A mode does not support the no mls qos rewrite ip dscp command for MPLS traffic, traffic
in IP in IP tunnels, and traffic in GRE tunnels.
To enable DSCP transparency, which preserves the received Layer 3 ToS byte, perform this task:
When you preserve the received Layer 3 ToS byte, QoS uses the marked or marked-down CoS value for
egress queueing and in egress tagged traffic.
This example shows how to preserve the received Layer 3 ToS byte and verify the configuration:
Router# configure terminal
Router(config)# no mls qos rewrite ip dscp
Router(config)# end
Router# show mls qos | include rewrite
QoS ip packet dscp rewrite disabled globally
Router#
Command Purpose
Step 1
Router(config)# no mls qos rewrite ip dscp
Disables egress ToS-byte rewrite globally on the router.
Router(config)# mls qos rewrite ip dscp
Enables egress ToS-byte rewrite globally on the router.
Step 2
Router(config)# end
Exits configuration mode.
Step 3
Router# show mls qos | include rewrite
Verifies the configuration.