DNS slow down performance

[VARITRONIX]

I know someone has posted the same questions before, but unfortunately I couldn't find them back for reference.

My problem goes like this, after I configure the "nsswitch.conf" to use both "file" & "dns" to resolve domain name, I then have trouble to telnet to my HP11.0 UX server. It sometimes takes more than 1 minute to connect, and it also slow down other connections. How can I solve this problem?

[Steven Sim Kok Leong]

Hi,

Can you verify that your entry in /etc/nsswitch.conf is:

hosts: files [NOTFOUND=continue] dns

Can you also verify that your /etc/resolv.conf contains the correct domain field?

If the telnet client is not registered in /etc/hosts, is it registered in the DNS? Is it registered for both forward and reverse resolution?

To confirm, perform an nslookup of both the client hostname as well as the IP address. Check whether there is a time difference between the nslookups. If so, check your RR records in the DNS.

Hope this helps. Regards.

Steven Sim Kok Leong
Brainbench MVP for Unix Admin
http://www.brainbench.com

[VARITRONIX]

First of all, thanks for your reply. Now I know that whenever a telnet session starts, UNIX will try to resolve the client hostname first.

However, can I skip this step? It's because I am using an external DNS, thus I have no control on it. I don't want to write all clients' IP into the hosts file (over 600, what a panic). Is there any other solution, or the only method I have left is to setup an internal DNS server?

[Sandip Samanta_3]

HI Vetronix,

First try to run nslookup & check hwo much time it takes to find out to get host ip address. If it is too much then try to configure one secondery DNS server in your end. Becs your primary DNS server is external.
If your nslookup result is satisfactory then change your nsswitch.conf . Put DNS entry before file entry.

Sandip

[Stephen Bouzan]

The delay you are experiencing is because of the name resolution. Solution: Run an internal DNS server and use the external as a backup. It is easy to set up a DNS server and adds many benefits. If your network is public then you might consider making your DNS server the master and the authoritative server a slave to you. Then you can manage your domain yourself. If your network is private then all the better. You and your clients will reslove quicker. Use BIND 8. Good Luck

[Nick Wickens]

I had exactly this problem yesterday and the issue was resolved with help from the Forums - See yesterdays entries under hp-ux -networking.

In my case I was using NT as Primary DNS server and the problem lay there but I guess if reverse lookups are not working under an HP-UX DNS server then the issue might be the same.