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I'm facing a problem with a Linux webserver of mine. It's a VM Ubuntu 10.4 LTS which runs a Wordpress network site. Out of the blue with no changes being made on the back end, ftp has stopped as has ssh. In addition, I cannot reach the host/site at all, but I can successfully ping it from inside the network... Similarly, I can do an nslookup just fine.

I'm very perplexed as to what's wrong. Below's a table of what's ok, which I hope might be useful to helpers.

Nslookup          YES
Ping              YES - Only within network
FTP               NO
SSH               NO
HTTP              NO - Apache, Mysql "appear" to be running fine though
Other Servers     YES
on Cluster ok
Ports open        YES - listening on all the necessary: 80, 22, 23, 25, 3306 etc.
Telnet            ??? - Ports 80, 3306 don't work, others do

From the above I've gathered it's to do with my box, well that was obvious, but seeing that DNS resolution is ok (internally at least) and how random services have gone down, I'm wondering if there has been some kid of bug or virus, or if the networking just broke out of the blue.

Many, many thanks in advance!

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Can you include the output from netstat -rn and netstat -tnlp? –  Arcege Mar 22 '12 at 19:38
    
But is the nameserver running on that very same machine? the fact DNS lookup works should mean the nameserver is OK, not that the machine is replying to incoming traffic... One interesting thing is that the only other thing that works is ping, which runs over ICMP, while ftp relies on UDP and both HTTP and ssh rely on TCP. I remember reading that connection tracking in iptables may cause legitimate requests to be dropped, but I doubt this is related at all. –  njsg Mar 22 '12 at 21:36
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1 Answer 1

Ok, very strange...

I've come back this morning and all of a sudden, it's all running again. I'm assuming there was some greater networking issue that affected that range or something. I seriously cannot recall anything I done that would have resolved this issue other than it was shutdown yet again! So now, everything on the above table can be stamped with a 'YES'. Thanks a lot for your input guys, will bare the connection tracking in mind and will learn more about netstat/telnet...

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