[c-nsp] Question about class-map, policy-map and TOS field?

Andy Saykao andy.saykao at staff.netspace.net.au
Mon Dec 15 20:25:50 EST 2008

Hi All,
We're trying to reduce the CPU on one of our core routers (7606)  by
using class-map and applying the policy-map to the interface rather then
the old PBR way of "ip policy route-map".
Here's our current config using the PBR way of doing things:
interface GigabitEthernet4/1/1
 bandwidth 1000000
 ip address A.B.C.D
 ip route-cache policy
 ip policy route-map TOS-TAG-IX
 load-interval 30
 no negotiation auto
route-map TOS-TAG-IX permit 10
 set ip tos 15
Basically all traffic coming in via this interface has their TOS field
set to 15. 
We've had an upsurge of traffic coming into this interface and this has
caused our CPU to shoot through the roof.
>From my research, PBR can be rather CPU intensive because packets are
process switched. We've been advised to use the new way of marking
traffic with class-map and policy-map.
What I don't get is - how do we set an ip tos value of 15 using
policy-map when that option doesn't exist (see below).
Router(config)#policy-map TOS-TAG-IX-POLICY
Router(config-pmap)#class TOS-TAG-IX-CLASS
Router(config-pmap-c)#set ip ?
  dscp        Set IP DSCP (DiffServ CodePoint)
  precedence  Set IP precedence

How do I set it so the incoming packets are marked with a TOS of 15 with

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