[CentOS] Wierd Networking Problem
shawn at tandac.com
Wed Oct 31 14:07:28 UTC 2007
On Wednesday 31 October 2007, Alain Spineux wrote:
> Did you tried to ping other host inside and outside your network, your
> gateway ? If not working, did you tried to arping your gateway ?
> Did you look for packet with "tcpdump -n -i eth0" ?
I can successfully traceroute from the server to google. I didn't try an
I'll review the tcpdump messages today and let you know...
> On 10/31/07, Shawn Everett <shawn at tandac.com> wrote:
> > Hi Guys,
> > I'm 100% sure this is not a Linux issue but I want a second opinion...
> > I have a Linux server running CentOS. It was been absolutely perfect
> > without any errors or problems.
> > Since Monday it has been unable to send email. It is configured to
> > act as a smart host. All email gets forwarded to smtp.isp.net.
> > The server is on a network behind a firewall completely nat'd. No
> > ports are forwarded to it.
> > telnet smtp.isp.net 25 generates the following:
> > Trying a.b.c.d...
> > Connected to smtp.isp.net.
> > Escape character is '^]'.
> > And then nothing. All other machines can connect to smtp.isp.net 25
> > without a problem. They also use that host for their outgong mail
> > server.
> > Using links to surf the web has a similar result. It just hangs
> > traceroute and nslookups work correctly.
> > There are no errors anywhere.
> > The network in question has various routing and vlan configurations,
> > proxy servers and such. I tend to suspect they're the problem.
> > They're also not in my control.
> > The firewall does show the Linux box attempting to make SMTP
> > connections but nothing else.
> > Any ideas or suggestions would be appreciated. I have not yet
> > rebooted the server.
> > Shawn
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