Secondry DNS

[akthar abdul jabbar]

Hi ..

How to configure secondry DNS in my server. Pls Help.

[Hoefnix]

edit the /etc/resolv.conf file like next:

search blbla.bla.com
nameserver
nameserver


Regards,

Peter

[G. Vrijhoeven]

HI,

Peter is right, but you can also use the domain string in /etc/resolv.conf.
Check man resolv.conf

Gideon

[Elmar P. Kolkman]

Do you mean to use a secondary DNS? Then Peter's solution is right.
If you mean: how do I configure my server to be a secondary DNS, it is more tricky.
You need to copy your named.conf file from the primary DNS, replace all 'master' entries to 'slave' entries, create the directory used for storing the database files, edit /etc/rc.config.d/namesvrs to start the named, etc.

Before going into more detail on this, explain what you want.

[akthar abdul jabbar]

Hi Thanks for quick response,

Do I Need to reboot the server after editing the resolv.conf or it takes effect automatically once I save the file

Akthar

[G. Vrijhoeven]

Hi,

No reboot, it should work right away.

Gideon

[akthar abdul jabbar]

Hi Elmar,

I want to use secondry DNS address , And I used Peter's suggestion and edited the resolv.conf file .. I have reboot the server or I have to start stop any deamon to take this to effect ??!!

Thanks again for all for useful inputs

Regards

Akthar

[Hoefnix]

If you want to test the changes, just swap 1st and 2nd nameserver in the resolv.conf (change the order in the file)and do an nslookup .

From the response you can figure out which DNS-server is used.

Regards,

Peter

[Elmar P. Kolkman]

Goodmorning Akhtar (though probably afternoon for you),

If you only want to use a secondary nameserver from the machine, you don't have to reboot. Every time a lookup is done on the server, /etc/resolv.conf is read for the order of DNS servers. Like Peter said you can test it directly.

[Jakes Louw]

Just check that you have set /etc/nsswitch.conf to include DNS as an option.

[D.Blond]

If you want to test the changes, just swap to 2nd nameserver in "nslookup" with the command "server".
Dominique

[Jakes Louw]

Or you could request the nslookup from a specific DNS server:

nslookup ipaddress dnsserver

eg: nslookup 165.143.128.21 dns2

[Sridhar Bhaskarla]

Hi,

Add another line that says "nameserver ip_address" to your /etc/resolv.conf.

DNS will be searched using the servers specified in the order in /etc/resolv.conf. There are couple of points to be noted.

1. As long as the first server responds, secondary name server will not be used.
2. If the first server does not respond, then the queries will go to next server in the order after the default "retrans" value. The retrans value is 5 seconds.
3. You can add the configurable parameters retrans and retry to /etc/resolv.conf to set the timeout. retrans is specified in milli seconds. For ex.,

domain yourdomain.com
nameserver 10.10.10.10
nameserver 10.10.10.20
retrans 2000
retry 2

The above will set the timeout to 2 seconds before the system call queries the next timeout.

4. There is no daemon like 'nscd' in hp-ux that will take care of automatically failing over to the next name server in the resolv.conf file in case the primary server does not respond. So each query has to go through the retrans timeout.

5. nslookup is not a 100% method to test the configuration in /etc/resolv.conf as it doesn't use gethostbyent() calls. But retrans is in effect for all the services that use gethostbyent() set of calls.

-Sri