Odd Network Problem with FC5+

Mikkel L. Ellertson mikkel at infinity-ltd.com
Thu Nov 15 14:20:51 UTC 2007

blake at ispn.net wrote:
> I seem to be having trouble sending mail from an FC5 server to
> mail.jococourthouse.com.
> The problem manifests itself as extreme slowness, which eventually leads
> to a timeout before I can even receive a full welcome prompt from the
> remote side.
> I have tested on ~ 10 boxes (different hardware) around the US ranging
> from FC5 through FC8 and NONE can telnet to this mx while RH, FC3 RH4,
> windows, and cisco gear on the same networks can ALL telnet without a
> problem.
> wireshark on the FC5 boxes show that the TCP handshake occurs as normal,
> however from then on all I receive from the remote side are 60 byte frames
> labeled 'TCP segment of a reassembled PDU' until I eventually receive an
> RST from the remote. - A capture on the working boxes looks normal.
> I suspect the problem is related to an IP/TCP change in the kernel or
> FC5+, however I have no idea what change could have occurred. Any insight
> or recommendations for resolving this problem would be appreciated.
> Thanks,
> -Blake
Dumb question - does it work properly when sending to other mail
servers? If so, I suspect that mail.jococourthouse.com is doing an
idend request on incoming mail connections, and this request is
being dropped instead of rejected by a firewall between the two
systems. This option is seldom used any more because it doesn't
really provide useful information. (It did when only mainframes were
connected to the Internet.) I don't think Fedora even installs an
ident daemon by default any more.


  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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