Setting DSCP value on GRE IP Header

[shay.kotian]

GRE Tunnel has been created between R1 and R2.

OSPF is running on all routers for reachability.

Clients are 1.1.1.1, 2.2.2.2 and 3.3.3.3.

The requirement:

On R1 using the GRE tunnel the packet 1.1.1.1 to 2.2.2.2 needs to traverse through R3-R5-R4 

On R1 using the GRE tunnel the packet 1.1.1.1 to 3.3.3.3 needs to traverse through R3-R6-R4

The routing needs to be based on the internal IP addresses and there is only one GRE tunnel

Solution thought:

Use DSCP to tag the traffic on R1 and create Route Maps on R3 to route the packet according.

Unfortunately, we are unable to set the DSCP value on the outer IP header. But we are able to set on the inner IP header.

Any alternate solution or change in config would be much appreciated.

[Georg Pauwen]

Hello,

my first thought was to play around with OSPF areas...

What areas do you have configured so far ?

[shay.kotian]

Hi Georg,

Thank you for the quick reply. Everything is in one area as of now.

[Joseph W. Doherty]

"Unfortunately, we are unable to set the DSCP value on the outer IP header. But we are able to set on the inner IP header."

Hmm, I thought it was possible to set the ToS on a GRE packet on the tunnel's source router. That said, if you can set the original packet's ToS, before its encapsulate, by default, the GRE packet should copy it.