topic Re: Secondry DNS in Operating System - HP-UX

Secondry DNS

akthar abdul jabbar — Mon, 19 Jan 2004 03:28:00 GMT

Hi ..

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

Re: Secondry DNS

Hoefnix — Mon, 19 Jan 2004 03:31:29 GMT

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

search blbla.bla.com
nameserver
nameserver

Regards,

Peter

Re: Secondry DNS

G. Vrijhoeven — Mon, 19 Jan 2004 03:35:43 GMT

HI,

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

Gideon

Re: Secondry DNS

Elmar P. Kolkman — Mon, 19 Jan 2004 03:37:01 GMT

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.

Re: Secondry DNS

akthar abdul jabbar — Mon, 19 Jan 2004 03:41:13 GMT

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

Re: Secondry DNS

G. Vrijhoeven — Mon, 19 Jan 2004 03:45:38 GMT

Hi,

No reboot, it should work right away.

Gideon

Re: Secondry DNS

akthar abdul jabbar — Mon, 19 Jan 2004 03:47:05 GMT

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

Re: Secondry DNS

Hoefnix — Mon, 19 Jan 2004 03:56:16 GMT

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

Re: Secondry DNS

Elmar P. Kolkman — Mon, 19 Jan 2004 04:10:47 GMT

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.

Re: Secondry DNS

Jakes Louw — Mon, 19 Jan 2004 04:40:31 GMT

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

Re: Secondry DNS

D.Blond — Mon, 19 Jan 2004 11:02:19 GMT

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

Re: Secondry DNS

Jakes Louw — Tue, 20 Jan 2004 00:58:20 GMT

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

nslookup ipaddress dnsserver

eg: nslookup 165.143.128.21 dns2

Re: Secondry DNS

Sridhar Bhaskarla — Tue, 20 Jan 2004 01:28:58 GMT

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