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  • Everything was working fine with server2 until I had to reboot.
  • Since reboot, I cannot SSH into the machine directly, and, http is not working...MOST of the time.
  • Every once in a while, randomly, I can suddenly get in. But most of the time, the connections time out.
  • I CAN SSH from server1 into server2. This always works, but access from the outside is sporadic at best.
  • Firewall is not blocking those ports and the ports always reply
  • WGET from server2 is timing out as well. Even when SSH and HTTP happens to work that particular minute, WGET never works.
  • I can only recommend the usual troubleshooting procedure: 1) check all logs + dmesg 2) telnet to service-ports and see what you get back 3) check with tcpdump at server-side / server+client-side / capture pcap and analyse with wireshark BTW: if server1 is on the same subnet you may potentially have a router/arp/firewall issue – powo May 2 '14 at 18:03
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The first few things I would check for are the following:

  • Does server2 have the correct network prefix and gateway address configured on the network interface?
  • Does arp -n on server2 show an entry for the gateway?
  • If possible, check arp -n on the gateway as well looking for an entry for server2.

Sporadic connectivity like you describe can happen in scenarios where arp request and replies between gateway and host is for some reason not working, but they can pick up each other's MAC address anyway by watching arp requests. In one such case I was able to temporarily work around the problem by pinging an unused IP address on the LAN from the problematic host, until I found the root case, which was conflicting RFC1918 addresses assigned on two different interfaces.

| improve this answer | |
  • Sound like the default gateway may be on the wrong interface. – bombcar May 2 '14 at 20:39
  • When I do arp -n on server2, the IP address that I use to SSH into it is NOT listed, but there are several similar ones. – Corepuncher May 3 '14 at 19:48

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