DNS resolver

[Teck Sim]

After I updated DNS resolver addresses on UNIX servers to new DNS server addresses, users are unable to log on to the servers.
My network guy told me that I have to restart the network services. What is that mean?
Thanks in advance.

[Sridhar Bhaskarla]

Hi,

What exactly were the changes you made to the server?. Can you give us one example?.

If you changed the server names to new IP addresses, then you will need to configure the hostname as well the new IP address on the server.

Make sure /etc/resolv.conf on the servers point to correct DNS resolvers.

-Sri

[Teck Sim]

I opened up the file /etc/resolv.conf
replaced current lines:

nameserver 172.xx.xx.xx
nameserver 172.xx.xx.xx

with

nameserver 172.00.xx.xx
nameserver 172.00.xx.xx

thanks.

[Bill Hassell · Accepted solution]

There is no need to do anything on your end as far as starting or restarting a service. nameserver resolution is realtime and the resolv.conf file is read for every request. Start by manually requesting a DNS server to provide you with an address with the command:

nslookup some-name dns-server's-IP-address

(in your example: nslookup some-name 172.0.xx.xx)

Did it work? If not, the DNS server is not reachable. Start with a ping to the DNS server's address. If it does not respond, then there is a big network problem in reaching the new DNS servers. If it does respond but nslookup fails, then the server is not responding to your requests for DNS responses.

Now if you do get a response using the above nslookup command, check /etc/resolv.conf, the first IP address listed. Is it the same as the one above? If yes, try nslookup without the dns-server's IP address as the 2nd parameter. Did it report that it can't resolve the DNS server's name? That is a big (but common) problem in the DNS server: it doesn't knwo it's own name! For security, all DNS servers must be able to resolve their own IP address into a name.

[Sridhar Bhaskarla]

On each server where you made changes, run 'nslookup' on the server name (command: hostname) and make sure they return the correct IP address that is configured on the server.

-Sri

[Pete Randall]

Could this be a routing issue? Like your default route is still pointing to 172.xx.xx.xx instead of 172.00.xx.xx?

Pete

[Arockia Jegan]

Hi Teck,

Did you do any changes in the /etc/nsswitch.conf file? If you copy the nsswitch.hp_defaults to nsswitch.conf file you will have this problem. Have a look at the /etc/nsswitch.conf file and make sure the source for your password is files (/etc/passwd).

[sven verhaegen]

Restarting networking on HP-UX can be done quiet simply by executing

/sbin/init.d/net stop

and

/sbin/init.d/net start

it will stop and restart the network subsets , meaning the rc startup scripting , just make sure that afterwards you control any left over routing entries pointing to old paths if any changes on lancard ip addresses where made and alter accordingly , any changes to DNS servers shoukd be instantanious however

[Wodisch]

Hi Teck,

I guess that system's FQDN (fully qualified domain name) has changed - due to different resolution from the new DNS server(s).
And since CDE store the name of the previously used hostname, it cannot access the screen with the old name, any more...
Move those users' "$HOME/.dt/" directories to another name (or remove them), and then let them try again - does is work now?

HTH,
Wodisch