XR Ttl Change

[AlanGregory]

Scenario: I need to change the ttl of packets coming out of pppoe interfaces.

Is there any option available in IOS XR?

[xthuijs]

that is interesting! yeah sorry there is no configuration today that can rewrite the TTL of the packets. every router is supposed to decrement by one, not adding it :) in fact sounds sort of dangerous too, because if there is a routing loop one could infinitely loop packets around without stopping...

xander

[AlanGregory]

In fact we need to set it to 2, to prevent routing continuity in a scenario of ours.

[xthuijs]

ah ok I see allen, yeah this is currently not a supported feature in PBR.

doing this in the hardware forwarding path is doable, but tricky, besides the ttl, the checksum needs to be updated as well. I assume that it needs to be done conditionally for some traffic categories only?

If you have an external device that has that capability, then you could possibly

leverage PBR to redirect traffic to that device, modify TTL and continue to route from there?

cheers

xander

[AlanGregory]

We're going to do it on client's cpe