Date: Thu, 5 Feb 2004 08:47:07 -0500 From: "Lee Dilkie" <lee@dilkie.com> To: "'Alexander Botov'" <alexb@mail.bg>, <freebsd-questions@freebsd.org> Subject: RE: forwarding with ttl=1 Message-ID: <00c301c3ebee$8c12ec20$c10133ce@dilkie.com> In-Reply-To: <004f01c3ebea$5974d750$0200a8c0@ALIENX>
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> > 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 ? > TTL (Time To Live) is a counter value in an IP packet that gets decremented by every "hop" (router). When it reaches a value of zero, the packet is discarded. Using a TTL of 1 isn't going to be very useful as your packets will all be discarded at the first router. This is working as intended. Normally, TTL is set to 128-ish.
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