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I relocated a Ubuntu 16.04 server to a new datacenter and can't get the network to work properly. I ended up upgrading it to 18.04 and changing from /etc/network/interfaces to netplan and the issue persists.

When trying to ping the gateway it gives an error, but then it works for a few times and then errors again. I have tried with multiple IP addresses making sure it isn't an IP conflict, I have also used multiple NIC interfaces with multiple wires plugged into different ports of the switch.

Earlier I had it working, it seemed that as long as ping was active it kept the connection alive and it stated up long enough to do the upgrade to 18.04, but since rebooting it still is having trouble. I tried using netplan but it still isn't working

I am not sure what to do next except format and reinstall which I would rather not do since it took quite some time to get it configured right with the OpenStreetMap setup that is on it.

➜  ~ ping  28.53.45.1                   
PING 28.53.45.1 (28.53.45.1) 56(84) bytes of data.
From 28.53.45.5 icmp_seq=1 Destination Host Unreachable
From 28.53.45.5 icmp_seq=2 Destination Host Unreachable
From 28.53.45.5 icmp_seq=3 Destination Host Unreachable
    .....
From 28.53.45.5 icmp_seq=29 Destination Host Unreachable
From 28.53.45.5 icmp_seq=30 Destination Host Unreachable
64 bytes from 28.53.45.1: icmp_seq=31 ttl=64 time=900 ms
64 bytes from 28.53.45.1: icmp_seq=32 ttl=64 time=0.532 ms
64 bytes from 28.53.45.1: icmp_seq=33 ttl=64 time=0.306 ms
64 bytes from 28.53.45.1: icmp_seq=34 ttl=64 time=2.09 ms
64 bytes from 28.53.45.1: icmp_seq=35 ttl=64 time=0.728 ms
64 bytes from 28.53.45.1: icmp_seq=36 ttl=64 time=0.243 ms
64 bytes from 28.53.45.1: icmp_seq=37 ttl=64 time=0.313 ms
64 bytes from 28.53.45.1: icmp_seq=38 ttl=64 time=0.350 ms
64 bytes from 28.53.45.1: icmp_seq=39 ttl=64 time=0.345 ms
64 bytes from 28.53.45.1: icmp_seq=40 ttl=64 time=8.61 ms
From 28.53.45.5 icmp_seq=41 Destination Host Unreachable 
   ......
From 28.53.45.5 icmp_seq=46 Destination Host Unreachable

Output of arp -a when it wasn't working:

➜  ~ arp -a
28-53-45-6.c7dc.com (28.53.45.6) at 6c:ae:8b:62:94:3c [ether] on eno1
? (28.53.45.2) at 74:8e:f8:75:aa:00 [ether] on eno1
? (192.168.2.6) at 6c:ae:8b:62:94:3b [ether] on eno2
? (28.53.45.1) at 02:e0:52:51:5a:d2 [ether] on eno1
? (28.53.45.4) at 00:21:9b:99:f1:49 [ether] on eno1
? (28.53.45.3) at 74:8e:f8:75:22:00 [ether] on eno1

Then the next time it worked for a few ping attempts and failed again.

➜  ~ arp -a
28-53-45-6.c7dc.com (28.53.45.6) at 6c:ae:8b:62:94:3c [ether] on eno1
28-53-45-2.c7dc.com (28.53.45.2) at 74:8e:f8:75:aa:00 [ether] on eno1
? (192.168.2.6) at 6c:ae:8b:62:94:3b [ether] on eno2
28-53-45-1.c7dc.com (28.53.45.1) at <incomplete> on eno1
28-53-45-4.c7dc.com (28.53.45.4) at 00:21:9b:99:f1:49 [ether] on eno1
28-53-45-3.c7dc.com (28.53.45.3) at 74:8e:f8:75:22:00 [ether] on eno1
➜  ~ 

the line with the gateway address and <incomplete> is where the ping worked. 28-53-45-6 and 192.168.2.6 are the IP of the computer I am using to SSH in

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  • Maybe some router/switch/hub is causing problems... Can any other OS's booted on the same computer (server) get a solid internet connection? Try a live USB/ISO, or a few different ones
    – Xen2050
    Dec 26, 2018 at 5:14
  • I have a 48 port switch installed in the cabinet, this is the only server that is having trouble. I have all 4 ports going to different sections of the switch, but only activate them one at a time to prevent any conflicts. I can try booting a different OS, but I am pretty sure it is a configuration problem, not a hardware problem which is why I am trying so hard to fix it remotely, seems I should be able to if I could just find what the issue is.
    – Alan
    Dec 26, 2018 at 6:02
  • Perhaps your arp protocol is being disrupted. Check the output of arp -a when it is working and not working. See if the MAC address for the gateway changes. Dec 26, 2018 at 6:08
  • I haven't used arp in my diagnostics before, I posted the output, do you see anything helpful?
    – Alan
    Dec 26, 2018 at 8:48

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