IP helper question

davemikolajczak · ‎07-17-2008

I am trying to setup ip helper for an older application. It turns out that the TTL in the broadcast packet is 1. Is there a way that the router can change the ttl by matching the packet on input?

bvsnarayana03 · ‎07-18-2008

Router doesnt forward broadcasts. The reason for using "helper-address" is to convert the broadcast frames to unicast to the ip mentioned in helper command.

paolo bevilacqua · ‎07-18-2008

Hi BVS, clearly the person that asked the question knows that already.

The specific question was instead if it is possible to correct a situation in which the packet to be "helped" has TTL 1. To my knowledge, that is not possible.

davemikolajczak · ‎07-18-2008

Thanks, yes that is what I meant. I had thought that a route map might be able to do that but apparently not

Giuseppe Larosa · ‎07-18-2008

Hello David,

if the application does not provide a TTL greater then 1 the only way I see is to use a L2 tunnel service like L2TPv3, EoMPLS or if possible some form of bridging over the WAN.

However, I don't know what fits your need and if any of these are viable solutions.

This is because if the router processes the packet at Layer3 it will not forward it as unicast for the TTL =1 and helper-address will be not able to work on these packets

Hope to help

Giuseppe