DSCP

[JamesIMillsII]

Do Cisco Routers (2851) strip or modify DSCP tagging?

[Karsten Iwen]

Whatever you want the router to do ... ;-)

By default, the DSCP is not touched. But with the help of MQC (Modular QOS CLI) you can tell the router to modify the DSCP as your needs.

[Joseph W. Doherty]

At Karsten notes, by default, Cisco routers, at least on their routed ports, just completely ignore the ToS field (unlike "older" Cisco switches, which when you enable QoS features on them, reset the IPPrec/DSCP to zero).

However, as many ISRs support Ethernet L2 and L2/L3 switch modules (not to be confused with routed Ethernet port modules), I'm unsure what they do, or not, by default to the ToS field.