Re: SOLVED -- Re: [EXIM] (un)blocking dynamic IP addresses […

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Author: James FitzGibbon
Date:  
To: Malcolm Beattie
CC: exim-users, david
Subject: Re: SOLVED -- Re: [EXIM] (un)blocking dynamic IP addresses [Was: A way to do this?]
* Malcolm Beattie (mbeattie@???) [990420 08:53]:

> hangs". What's happening is that the client sends larger and larger
> packets with the "Don't Fragment" bit set so that, when the maximum
> MTU is reached, it'll get back an "ICMP Frag Needed" packet and thus
> know the optimum MTU. If some idiot has configured a firewall or
> router wrongly and drops all ICMP on the floor then the "ICMP Frag
> Needed" never arrives and the client thinks the packet has just
> been a random drop and keeps resending.


Using a combination of tcpdump/tcpshow, it should be pretty simple to verify
if this is the case. Having a copy of "TCP/IP Illustrated Volume 1" would
also be a great help.

--
j.

James FitzGibbon (JF647)                                        james@???
EHLO Solutions                                       Voice/Fax +1 416 410-0100


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