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Date:      Wed, 12 Mar 2008 17:39:23 +0200
From:      Nikos Vassiliadis <nvass@teledomenet.gr>
To:        freebsd-questions@freebsd.org
Cc:        Zbigniew Szalbot <zszalbot@gmail.com>, Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
Subject:   Re: traceroute problems
Message-ID:  <200803121739.24408.nvass@teledomenet.gr>
In-Reply-To: <20080310232639.K7504@wojtek.tensor.gdynia.pl>
References:  <94136a2c0803101454l6ca76c99ma1fa1083d7ea2137@mail.gmail.com> <94136a2c0803101520p4f044ce4lae76975f899296e7@mail.gmail.com> <20080310232639.K7504@wojtek.tensor.gdynia.pl>

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On Tuesday 11 March 2008 00:30:05 Wojciech Puchar wrote:
> > Right - thanks. I will see if I can unblock it then.

Hm, I wouldn't bet on it, since most of these devices tend
to have preconfigured well-hidden firewall rules.

> traceroute uses UDP packets, no special port numbers.

FreeBSD's traceroute can use TCP or ICMP instead of UDP.
You can also force using a specific port, so you can mimic a
web browser that uses an insanely small TTL. Something like:
"-e -P TCP -p 80 $destination_host"
or "-P ICMP $destination_host"
I've had success using combinations like the above.

Of course, if your NAT device drops ICMP indistinctively
or does not relate these ICMP to your LAN address, you're
out of luck. I think many DLinks are Linux based, so there is
good possibility to have a proper TCP/IP stack and a proper
packet filter. Can't tell of the packet filter rules though.

HTH, Nikos



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