1

I recently started maintaining a server which hosts personal domains of some people in my company.

For over than a month, I have started noticing simultaneous problems with services like sshd and httpd. I looked at the logs of both services and found nothing of note. I tried to find a pattern but couldn't have noticed any. When the error occurs;

  • Web pages become inaccessible

web page

  • Also, trying to connect to server via ssh fails with the following warning

enter image description here

These errors get resolved only after a reboot.

I am not an experienced system administrator and I know that the information I present is not enough. So, if some experienced friends out there want to help me out and require additional information, just say so and I'll provide.

2

What you described suggests a duplicate IP address in your network. You may want to start up a screen session on a few of the trouble servers and occasionally append the output of arp -an to a file. Your network engineers may also be able to spot this looking at the arp entries on each interface.

You can also use ssh-keyscan to make a list of known ssh fingerprints. This can also sometimes spot those conflicting IP addresses. In a worse case scenerio, this could also be an attempt at a MITM attack via arp poisoning, but I would not panic until you have more data.

If this turns out to be a dupe IP issue, there are short term work arounds you can do using arping to get your IP back, until folks sort out the problem. Sometimes this happens when DHCP pools are too small and/or lease times are too long for the size and usage of the network.

  • It indeed was caused by an IP conflict. Thank you very much. You saved my job :) – 0x5f3759df Dec 26 '16 at 9:32
  • Glad things worked out. Merry Xmas and happy new year :-) – Aaron Dec 27 '16 at 20:15

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