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Date:      Wed, 14 Feb 2007 00:51:57 +0200
From:      Alexander Motin <mav@alkar.net>
To:        Stephen.Clark@seclark.us
Cc:        freebsd-net@freebsd.org
Subject:   Re: pmtud problem
Message-ID:  <45D2410D.70509@alkar.net>
In-Reply-To: <1171401795.00688172.1171391400@10.7.7.3>
References:  <1171398196.00688135.1171386001@10.7.7.3> <1171398210.00688151.1171387801@10.7.7.3> <1171401795.00688172.1171391400@10.7.7.3>

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Stephen Clark wrote:
>>> if the pc sends a packet of 1460 bytes with the DF bit set shouldn't the
>>> freebsd 4.9 system
>>> send back an icmp dest unreachable - fragmentation needed and DF bit 
>>> set?
>>
>> Are you blocking icmp with a firewall filter?
>>
> Good  question - but the answer is no. The other interesting fact is 
> when I drop the mtu on
> the gre to 1412 I do see the icmp messages.

Are you using any dummynet shapes? There is ancient bug in dummynet, 
which leads to not sending of ICMPs when shape used on outgoing interface.

-- 
Alexander Motin mav@alkar.net
Optima Telecom



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