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Old 07-18-2016, 11:05 AM   #1
Registered: Oct 2012
Location: Belgium
Distribution: Xubuntu
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several times a day "server DNS address could not be found" for 5 mins (Xen-Hosted Debian)


I have a running owncloud-server on debian Jessie 8.1.
The server is reachable with a DNS name.
The router is setup to forward port 8080 to the owncloud-server which is hosted by a Xen7 server.

When I have an owncloud session open, every now and then the connection is lost and a "server DNS address could not be found".

When I perform a ping (from a ssh-session on a machine outside my own network) to the DNS name, I get a reply.

I tried doing nmap -p 8080 on the server which showed it as 'up', but I'm not sure it this is the router answering or the server ?

Internally I never loose the connection with this server (I have a owncloud-sync client pointed to the internal address of the server and it always works)

So, where should I begin to look for the problem here ?

Actually, when I begin to think of it, it might be a bad configuration of the DNS. This same server also acts as a DNS and has a second NIC enabled. At first with no purpose, but I discovered that the owncloud server was reachable with its public DNS name when the second NIC got an ipaddress from the DHCP (hence, from itself).
I suppose that way it registers it's name in the DNS ?
Could this be the source of the problem ?
Old 07-19-2016, 10:30 AM   #2
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Location: Massachusetts, USA
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You need to be a little more specific about your configuration. Are you running bind? Can you share the relevant parts of named.conf? Also:

grep hosts /etc/nsswitch.conf
cat /etc/resolv.conf 
ip route show


dns, network connectivity, nmap

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