I'm having a strange problem with a server I have sitting at my workplace (it's behind a NAT, if that's important). The issue is that at some times, it becomes unreachable and then comes back up again, usually within a few seconds, sometimes lasting up to 1 minute. It doesn't reboot, it doesn't crash. It simply becomes inaccessible. During this time, I cannot ssh into it, nor can I access any applications running on the machine (it's running a couple of Rails apps, so they become unreachable as well). I checked dmesg and saw these lines -
[ 4.958074] ADDRCONF(NETDEV_UP): eth0: link is not ready [ 5.040476] ADDRCONF(NETDEV_UP): eth1: link is not ready [ 5.175624] igb: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX [ 5.177207] ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
A couple of lines later, I see something similar concerning the network interfaces -
[1195777.544167] igb: eth0 NIC Link is Down [1195780.962943] igb: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
It does look like a network issue. /var/log/messages doesn't show anything interesting. I'm not sure how to debug this. Any clue as to what it could be? And what all things should I be checking here? Thanks!