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
Shawn Everett 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.
Anything happen around that time?
Any firewall rules on that box?
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" ?
On 10/31/07, Shawn Everett shawn@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 _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
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 arping.
I'll review the tcpdump messages today and let you know...
Shawn
On 10/31/07, Shawn Everett shawn@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 _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
On Oct 31, 2007 12:24 AM, Shawn Everett shawn@tandac.com wrote:
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.
Have you contacted "isp.net", whoever they are, to make sure that they have not blackholed or tarpitted that particular machine's IP address for some reason?
Bart Schaefer wrote:
On Oct 31, 2007 12:24 AM, Shawn Everett shawn@tandac.com wrote:
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.
Have you contacted "isp.net", whoever they are, to make sure that they have not blackholed or tarpitted that particular machine's IP address for some reason?
He said that the box is behind a nat and only that box behind the nat has a problem. I doubt that it has been specifically targetted by ip.
Have you contacted "isp.net", whoever they are, to make sure that they have not blackholed or tarpitted that particular machine's IP address for some reason?
He said that the box is behind a nat and only that box behind the nat has a problem. I doubt that it has been specifically targetted by ip.
I've narrowed things down to not include the Linux box. :)
I took the Linux box's IP and moved it to another non Linux machine. The same issues occur.
I have the network guy reviewing things.
Shawn
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Alain Spineux -
Bart Schaefer -
Christopher Chan -
Shawn Everett