Ubuntu 16.04 cannot resolve dns - connection timed out; no servers could be reached

[MarkHaysHarris777]

Hi,

I'm running Ubuntu 16.04 (Linux pine64 3.10.104-2-pine64-longsleep) for a few days on my Pine64 2GB. What I notice is that after a reboot DNS works fine, but after sometime DNS is no longer able to resolve. 

When DNS fails I get a message like:

nslookup www.google.com
;; connection timed out; no servers could be reached

However, if I reboot the Pine64 DNS works like a charm. 

I've got a fixed IP defined in /etc/network/interfaces.d/eth0
auto eth0
#iface eth0 inet dhcp
iface eth0 inet static
address 192.168.1.158
netmask 255.255.255.0
gateway 192.168.1.1
dns-nameservers 8.8.8.8


Which works because ifconfig shows the following:

eth0      Link encap:Ethernet  HWaddr 4a:7c:01:2a:0d:57
          inet addr:192.168.1.158  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::487c:1ff:fe2a:d57/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:172911 errors:0 dropped:9 overruns:0 frame:0
          TX packets:84150 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:28673200 (28.6 MB)  TX bytes:26435938 (26.4 MB)
          Interrupt:114


ip route shows the following:
default via 192.168.1.1 dev eth0 onlink
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.158

Does anybody have a suggestion where I should look for the rootcause/solution?

hi, try adding an automated ping to the nameserver ( temporarily ) to see if it helps.

Setup a crontab entry to run a script containing something like the following:

ping -c 3  <nameserveraddress>

( or similar.,  its a counted ping to the nameserver ip address )

Have the crontab entry ping the server every thirty minutes or an hour and see if that helps.  If so, you need to find out why things are going to sleep.  It would not hurt at all to maintain the ping in crontab forever.