DNS, resolution with second dns-server doesn't work

[centurion]

We have three dns servers in our resolv.conf:

nameserver 10.200.210.7 (internal)
nameserver 10.120.3.56 (external)
nameserver 193.28.97.130 (internal)

Some servers we have to resolv with the external server. But it doesn't work. When I resolv the adress manual, it works:

nslookup 10.120.3.56

Any ideas?

[Ganesan R]

Hi,

As far as I know, DNS will try with first nameserver listed in resolv.conf and it will not go to the next server until or unless the first server is unavailable.

If this is the case you need to change the order in resolv.conf based on your requirment. You need to put the server first which is resolving most of the hosts.

you can put the remaining entries in your /etc/hosts file as a workaround.

[Ivan Krastev]

Try with nsquery to check nsswitch.conf:

nsquery hosts "dns [NOTFOUND=continue]"


regards,
ivan

[centurion]

The most servers we resolv over the first and third one. And someone over the second.. :-(

[centurion]

root@smallville [/]# nsquery hosts 10.128.0.109 "dns [NOTFOUND=continue]"

Using "dns [NOTFOUND=continue]" for the hosts policy.

Searching dns for 10.128.0.109
10.128.0.109 was NOTFOUND

Switch configuration: Allows fallback

All name services have been searched

[TTr]

The resolver functions as expected. From "man 4 resolver":
...The algorithm used is: Try a name server; if the query times out, try the next and continue until all name servers have been tried, then repeat trying all the name servers until a maximum number of retries have been made...
This means that the second server (external) only gets queried if the first server does not respond. If the first server responds with a negative answer, then that's your answer.
To set up external name resolution, you only use the two internal nameservers in the resolv.conf file. then in these internal DNS servers you forward all nonlocal requests to the external DNS server. Check out the BIND manuals for details, the configuration varies with different versions of bind.
Talk you your DNS admin if it is not you about external resolution.

[TTr]

The "NOT FOUND=continue" is a directive to continue from the DNS name service to other name services such as hosts, nis, ldap that may be setup in the nsswitch.conf file. It does not direct the resolver to continue to the other nameservers in the resoolv.conf file.
Puting the external host names and IPs that you need to resolve in in your local /etc/hosts file is a workaround but it is not a formal external name resolution method.

[centurion]

I talk to our dns-admin ..

[centurion]

we make entries in the /etc/hosts and remove the external dns-server..