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I have a problem with my website (http://www.visikid.pl and www.visikid.com). I have webmin and virualmin. I have one domain as alias, and this alias (host: www.visikid.com) sometimes is unavailable for several minutes. It's probably DNS problem because chrome shows 105 (net::ERR_NAME_NOT_RESOLVED).

How can I troubleshoot this problem?

What can cause that only sometimes website is unavailable for several minutes (DNS problem)?

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Can you give us the domain in question? –  Nathan Adams Mar 9 '10 at 19:40

4 Answers 4

up vote 1 down vote accepted

First, ns1.visikid isn't found on the general internet:

tsavo:~ mcd$ host -t any visikid.com ns1.visikid.com
host: couldn't get address for 'ns1.visikid.com': not found

Your nameserver appears to be answering, but, has an SOA record that points to timesolutions.timesolutions.pl rather than ns1.visikid.com/ns2.visikid.com:

tsavo:~ mcd$ host -t any visikid.com 213.239.222.20
Using domain server:
Name: 213.239.222.20
Address: 213.239.222.20#53
Aliases: 

visikid.com mail is handled by 30 ASPMX3.GOOGLEMAIL.com.
visikid.com mail is handled by 30 ASPMX4.GOOGLEMAIL.com.
visikid.com mail is handled by 30 ASPMX5.GOOGLEMAIL.com.
visikid.com mail is handled by 10 ASPMX.L.GOOGLE.com.
visikid.com mail is handled by 20 ALT1.ASPMX.L.GOOGLE.com.
visikid.com mail is handled by 20 ALT2.ASPMX.L.GOOGLE.com.
visikid.com mail is handled by 30 ASPMX2.GOOGLEMAIL.com.
visikid.com descriptive text "v=spf1 a mx include:aspmx.googlemail.com include:_spf.google.com ~all"
visikid.com has SOA record timesolutions.timesolutions.pl. root.timesolutions.timesolutions.pl. 1265887100 10800 3600 604800 38400
visikid.com name server timesolutions.timesolutions.pl.
visikid.com has address 213.239.222.20
tsavo:~ mcd$ host -t ns visikid.com 8.8.8.8
Using domain server:
Name: 8.8.8.8
Address: 8.8.8.8#53
Aliases: 

visikid.com name server timesolutions.timesolutions.pl.

but, that domain isn't configured:

tsavo:~ mcd$ host timesolutions.timesolutions.pl
Host timesolutions.timesolutions.pl not found: 3(NXDOMAIN)

$ host timesolutions.timesolutions.pl. 213.239.222.20
Using domain server:
Name: 213.239.222.20
Address: 213.239.222.20#53
Aliases: 

Host timesolutions.timesolutions.pl not found: 5(REFUSED)

Adjust your SOA record on visikid.com, or fix the ACL for timesolutions.pl if you're going to continue using it.

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Thanks! Just add timesoltuions.pl zone: $ttl 38400 timesolutions.pl. IN SOA timesolutions.pl. team.timecamp.com. ( 1268245688 1200 3600 604800 38400 ) timesolutions.pl. IN NS timesolutions.pl. timesolutions.pl. IN A 213.239.222.20 timesolutions.timesolutions.pl. IN A 213.239.222.20 www.timesolutions.pl. IN A 213.239.222.20 –  Kamil Rudnicki Mar 10 '10 at 19:11

You can use dig or nslookup (on windows) to a DNS lookup for your domain name:

dig myhost.example.com

or

nslookup myhost.example.com

If the name does not resolve to an IP, you might want to report his problem to your DNS provider.

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Use "dig@dns_server myhost.example.com" to query a specific DNS server. –  John Gardeniers Mar 9 '10 at 3:04
    
This is a long and painful process. Better to use a tool which automates the most common tests like Zonecheck. –  bortzmeyer Mar 12 '10 at 8:10

Cory has the right idea, but that will only query YOUR ISP's DNS servers, NOT the DNS server for your domain.

A couple of suggestions: Are you able to get to other websites while your website is having DNS issues? Find out all the DNS servers for your domain, and when you are having problems query each DNS server to find the one that isn't responding. If none of them are responding, yet you can still query other DNS servers, then you need to report this to your hoster.

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Yes I'm able to get to other websites (visikid.pl) while my website is having DNS issues (visikid.com). I have a BIND DNS server on my machine. It pretty strange problem... –  Kamil Rudnicki Mar 9 '10 at 6:57

Using any DNS testing tool will show you your problems. The biggest: there is only one name server for visikid.pl. If there is any problem with it (network, machine, whatever), the domain disappears.

This is the first fatal error reported by Zonecheck:

% zonecheck visikid.pl 
ZONE  : visikid.pl.
NS <= : timesolutions.timesolutions.pl. [213.239.222.20]
NS    : ns1.visikid.pl. [213.239.222.20]
NS    : ns2.visikid.pl. [213.239.222.20]

   _____________
 ,-------------.|
~~~~ |    fatal    || ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 `-------------'
f> All addresses should be distinct
 | Adv: ZoneCheck
 |   To avoid losing all connectivity with the authoritative DNS in case
 | of network outage it is advised to host the DNS on different networks.
 | 
 | Ref: IETF RFC2182 (Abstract)
 |   The Domain Name System requires that multiple servers exist for every
 | delegated domain (zone). This document discusses the selection of
 | secondary servers for DNS zones. Both the physical and topological
 | location of each server are material considerations when selecting
 | secondary servers. The number of servers appropriate for a zone is also
 | discussed, and some general secondary server maintenance issues
 | considered.
 `----- -- -- - -  -
 :   The nameservers timesolutions.timesolutions.pl., ns1.visikid.pl.,
 : ns2.visikid.pl. are using the same IP address (213.239.222.20).
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