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I have this remote Ubuntu 12.04 minimal headless server which I access and manage over reverse-SSH-tunnel (because it's behind a NAT firewall).

However, the issue I'm facing is, that randomly it cannot be accessed, whether remotely or over the LAN. When I say random,at times it can go for days and at times it doesn't go for more than 24hrs.

At first I thought it was maybe a power-saving thing or maybe the UPS having a problem or maybe even a hardware issue with the server itself, so I asked a guy on-site to make some observations:

  • Server is not powering off
  • server is not going into power saving mode
  • I asked the guy there to press the power button and the server nicely shut down and powered off, so it had not crashed or frozen
  • Then he pressed the power button again and the server booted up, connected to the internet and I could immediately access it over reverse-SSH-tunnel

I suspected that it could be a random clash of IP number - maybe the IP number assigned could have been in use previously and maybe an issue. I also suspected some hardware issue with the network card. So I set a background continuous ping command

ping 173.194.47.23 -i 600 >> ping.txt &

The result was, that after 48hrs I got 140 lines of which the first 136 lines were responses and the remaining 4 lines we, "Destination Host Unreachable". Seeing that I had set the ping interval to 600 and there are 140 files, I can see the command went on for about 23.5hrs Here's the results of ping.txt:

PING 173.194.47.23 (173.194.47.23) 56(84) bytes of data.
64 bytes from 173.194.47.23: icmp_req=1 ttl=52 time=236 ms
64 bytes from 173.194.47.23: icmp_req=2 ttl=52 time=231 ms
64 bytes from 173.194.47.23: icmp_req=3 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=4 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=5 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=6 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=7 ttl=52 time=232 ms
64 bytes from 173.194.47.23: icmp_req=8 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=9 ttl=52 time=232 ms
64 bytes from 173.194.47.23: icmp_req=10 ttl=52 time=234 ms
64 bytes from 173.194.47.23: icmp_req=11 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=12 ttl=52 time=228 ms
64 bytes from 173.194.47.23: icmp_req=13 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=15 ttl=52 time=220 ms
64 bytes from 173.194.47.23: icmp_req=16 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=17 ttl=52 time=229 ms
64 bytes from 173.194.47.23: icmp_req=18 ttl=52 time=236 ms
64 bytes from 173.194.47.23: icmp_req=19 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=20 ttl=52 time=235 ms
64 bytes from 173.194.47.23: icmp_req=21 ttl=52 time=217 ms
64 bytes from 173.194.47.23: icmp_req=22 ttl=52 time=219 ms
64 bytes from 173.194.47.23: icmp_req=23 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=24 ttl=52 time=220 ms
64 bytes from 173.194.47.23: icmp_req=25 ttl=52 time=222 ms
64 bytes from 173.194.47.23: icmp_req=26 ttl=52 time=218 ms
64 bytes from 173.194.47.23: icmp_req=28 ttl=52 time=240 ms
64 bytes from 173.194.47.23: icmp_req=29 ttl=52 time=224 ms
64 bytes from 173.194.47.23: icmp_req=30 ttl=52 time=230 ms
64 bytes from 173.194.47.23: icmp_req=31 ttl=52 time=221 ms
64 bytes from 173.194.47.23: icmp_req=32 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=34 ttl=52 time=224 ms
64 bytes from 173.194.47.23: icmp_req=35 ttl=52 time=277 ms
64 bytes from 173.194.47.23: icmp_req=36 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=37 ttl=52 time=216 ms
64 bytes from 173.194.47.23: icmp_req=38 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=39 ttl=52 time=217 ms
64 bytes from 173.194.47.23: icmp_req=40 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=41 ttl=52 time=685 ms
64 bytes from 173.194.47.23: icmp_req=42 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=43 ttl=52 time=233 ms
64 bytes from 173.194.47.23: icmp_req=44 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=45 ttl=52 time=242 ms
64 bytes from 173.194.47.23: icmp_req=46 ttl=52 time=239 ms
64 bytes from 173.194.47.23: icmp_req=47 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=48 ttl=52 time=229 ms
64 bytes from 173.194.47.23: icmp_req=49 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=50 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=51 ttl=52 time=238 ms
64 bytes from 173.194.47.23: icmp_req=52 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=53 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=54 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=55 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=57 ttl=52 time=233 ms
64 bytes from 173.194.47.23: icmp_req=58 ttl=52 time=228 ms
64 bytes from 173.194.47.23: icmp_req=59 ttl=52 time=229 ms
64 bytes from 173.194.47.23: icmp_req=61 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=62 ttl=52 time=221 ms
64 bytes from 173.194.47.23: icmp_req=63 ttl=52 time=222 ms
64 bytes from 173.194.47.23: icmp_req=64 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=65 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=66 ttl=52 time=218 ms
64 bytes from 173.194.47.23: icmp_req=67 ttl=52 time=208 ms
64 bytes from 173.194.47.23: icmp_req=68 ttl=52 time=220 ms
64 bytes from 173.194.47.23: icmp_req=69 ttl=52 time=216 ms
64 bytes from 173.194.47.23: icmp_req=70 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=71 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=72 ttl=52 time=221 ms
64 bytes from 173.194.47.23: icmp_req=73 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=74 ttl=52 time=209 ms
64 bytes from 173.194.47.23: icmp_req=75 ttl=52 time=207 ms
64 bytes from 173.194.47.23: icmp_req=76 ttl=52 time=214 ms
64 bytes from 173.194.47.23: icmp_req=77 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=78 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=79 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=80 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=81 ttl=52 time=213 ms
64 bytes from 173.194.47.23: icmp_req=82 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=83 ttl=52 time=203 ms
64 bytes from 173.194.47.23: icmp_req=84 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=85 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=86 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=87 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=88 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=89 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=90 ttl=52 time=203 ms
64 bytes from 173.194.47.23: icmp_req=91 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=92 ttl=52 time=212 ms
64 bytes from 173.194.47.23: icmp_req=93 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=94 ttl=52 time=207 ms
64 bytes from 173.194.47.23: icmp_req=95 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=96 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=97 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=98 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=99 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=100 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=101 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=102 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=103 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=104 ttl=52 time=204 ms
64 bytes from 173.194.47.23: icmp_req=105 ttl=52 time=205 ms
64 bytes from 173.194.47.23: icmp_req=106 ttl=52 time=206 ms
64 bytes from 173.194.47.23: icmp_req=107 ttl=52 time=216 ms
64 bytes from 173.194.47.23: icmp_req=108 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=109 ttl=52 time=221 ms
64 bytes from 173.194.47.23: icmp_req=110 ttl=52 time=224 ms
64 bytes from 173.194.47.23: icmp_req=111 ttl=52 time=224 ms
64 bytes from 173.194.47.23: icmp_req=112 ttl=52 time=226 ms
64 bytes from 173.194.47.23: icmp_req=113 ttl=52 time=212 ms
64 bytes from 173.194.47.23: icmp_req=114 ttl=52 time=218 ms
64 bytes from 173.194.47.23: icmp_req=115 ttl=52 time=208 ms
64 bytes from 173.194.47.23: icmp_req=116 ttl=52 time=209 ms
64 bytes from 173.194.47.23: icmp_req=117 ttl=52 time=211 ms
64 bytes from 173.194.47.23: icmp_req=118 ttl=52 time=210 ms
64 bytes from 173.194.47.23: icmp_req=119 ttl=52 time=215 ms
64 bytes from 173.194.47.23: icmp_req=120 ttl=52 time=227 ms
64 bytes from 173.194.47.23: icmp_req=121 ttl=52 time=229 ms
64 bytes from 173.194.47.23: icmp_req=122 ttl=52 time=222 ms
64 bytes from 173.194.47.23: icmp_req=123 ttl=52 time=237 ms
64 bytes from 173.194.47.23: icmp_req=124 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=125 ttl=52 time=224 ms
64 bytes from 173.194.47.23: icmp_req=126 ttl=52 time=219 ms
64 bytes from 173.194.47.23: icmp_req=127 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=128 ttl=52 time=223 ms
64 bytes from 173.194.47.23: icmp_req=129 ttl=52 time=225 ms
64 bytes from 173.194.47.23: icmp_req=130 ttl=52 time=242 ms
64 bytes from 173.194.47.23: icmp_req=131 ttl=52 time=240 ms
64 bytes from 173.194.47.23: icmp_req=132 ttl=52 time=246 ms
64 bytes from 173.194.47.23: icmp_req=133 ttl=52 time=235 ms
64 bytes from 173.194.47.23: icmp_req=134 ttl=52 time=231 ms
64 bytes from 173.194.47.23: icmp_req=135 ttl=52 time=229 ms
64 bytes from 173.194.47.23: icmp_req=136 ttl=52 time=223 ms
From 192.168.0.10 icmp_seq=137 Destination Host Unreachable
From 192.168.0.10 icmp_seq=138 Destination Host Unreachable
From 192.168.0.10 icmp_seq=139 Destination Host Unreachable
From 192.168.0.10 icmp_seq=140 Destination Host Unreachable

The funny thing is, why did the pinging stop after 4 unreachables? The server remained ON; it had not crashed; it had not gone into sleep mode.

All other machines on the LAN are Windows based and there's not tech-guys on-site.

Any help and suggestions on how to handle and fault-find this, would be highly appreciated.

share|improve this question
    
Can you get the messages log from that time, it would be interesting to see if the system logs any sort of conflicts.. –  NickW Feb 18 '13 at 14:56
    
Hi NickW. Can you give some references,pls. –  user93078 Feb 18 '13 at 15:02
    
Well, you should have a /var/log/ directory and there may be either a messages, or system log file located in there. If you have a look in there, at around the time the ping stopped functioning, I'd be really surprised if there wasn't some sort of error logged. –  NickW Feb 18 '13 at 15:03
    
maybe provide a few details about the server hardware (motherboard type/model). we're facing similar issues with supermicro X7SPA-HF boards where eth0 sometimes just disappears after a few days. –  Gryphius Feb 18 '13 at 15:09
    
Calculating, it works out the last process in the ping took place at about 14:02 (17th Feb), so I followed your instructions and see a syslog.1 file in /var/log and in there at about 14:02 is: Feb 17 14:02:47 dhclient: last message repeated 4 times However,way back at about 13:29, issues seem to have started as autossh has been unable to connect.But I still can't figure out where the problem lies;I am however getting a feeling that it's to do with renewing the IP number? I've uploaded a portion of the syslog.1 file which I feel links to the problem link –  user93078 Feb 18 '13 at 20:02

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