Re: Can't connect to windows box from Debian, can from Red Hat

[Andreas Janssen <andreas.janssen@bigfoot.com>]

Hello

Marc Stein (<mstein@egrad.com>) wrote:

> This is a really bizarre situation.  I have not been able to send mail
> to a specific Windows mail server at cw2.coreweb.com from a Postfix
> server on Debian.
>
> I cannot telnet to port 25 on the Windows machine from any Debian box
> that I have. I can telnet to the machine from Red Hat and Windows 
> machines. When I send a telnet request from the Debian box I don't get 
> a reply and the telnet request times out.  
> 
> What makes this particularly puzzling (to me, at least) is that the
> Debian, Red Hat, and Windows boxes that I try to telnet from can all
> be in the same subnet so it doesn't seem that it could be a firewall
> issue on the other end.
> 
> An example follows:
> 
> [...]
> 28903   2.336422 linux-dev.y2m.com -> cw2.coreweb.com TCP 33038 >
> telnet [SYN, ECN, CWR] Seq=3827497024 Ack=0 Win=5840 Len=0

Try to turn off ECN:

echo 0 > /proc/sys/net/ipv4/tcp_ecn

best regards
        Andreas Janssen


-- 
Andreas Janssen <andreas.janssen@bigfoot.com>
PGP-Key-ID: 0xDC801674
Registered Linux User #267976
http://www.andreas-janssen.de/debian-tipps.html