forwarding with ttl=1

Alexander Botov alexb at
Thu Feb 5 05:16:11 PST 2004

Hi All 

I am newbie with configuring networks under FreeBSD . I have small network with gateway running on FreeBSD 5.2 Release .My ISP offers me pppoe service for connecting to Internet . I didn't have problems with configuring ppp with pppoe . I used nat option wchich works fine for masquerading the local network from the world . The problem is that the ISP's gateway returns every time packets with ttl=1 which makes further forwarding impossible . My gateway returns icmp error mesage "time exceeded" and discards packets . I want to know if I made some mistake with configuring nat service or if not what is the solution of the problem ? Is there any service that can increment ttl and process the packet ? I tried to avoid the checking of ttl in the ip_forward() function in ip_input.c and skipping the decrement of ttl and everything works fine but i think that this is very ugly kernel hack . Probably there is an easy and elegant solution . Any ideas ?

please excuse my English 

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