topic Re: name resolution from DNS server in Operating System - HP-UX

name resolution from DNS server

Jorge Prado T — Fri, 07 Apr 2006 10:25:01 GMT

HI,
Because when the resolution of names is enabled from a dns microsoft, the login process is very slow?
S:O HP-UX 11i

Thanks in advance

Jorge Prado T.

Re: name resolution from DNS server

Ivan Ferreira — Fri, 07 Apr 2006 10:26:59 GMT

Are you login using telnet or secure shell?. Maybe the reverse lookup is slowing the login prompt.

Re: name resolution from DNS server

Uday_S_Ankolekar — Fri, 07 Apr 2006 11:00:34 GMT

check /etc/resolv.conf file. You should have domain nameserver address there

domain yourdomainname
nameserver x.x.x.x

-USA..

Re: name resolution from DNS server

Ivan Ferreira — Fri, 07 Apr 2006 11:02:37 GMT

If you use SSH, try configuring /etc/rc.config.d/sshd

SSHD_START=1
SSHD_ARGS="-u0"

Re: name resolution from DNS server

Anil C. Sedha — Fri, 07 Apr 2006 11:06:51 GMT

Jorge,

I would suggest that you verify the routing first for your DNS Server. On Windows run the following

tracert DNSSERVERNAME or

tracert IP

On UNIX run,

traceroute DNSSERVERNAME or IP

---

then if the number of hops seem acceptable to you (should be just 2 or max 3) then add your servers directly in the /etc/resolv.conf file to resolve DNS names through the system than by the DNS server first.

vi /etc/resolv.conf

Add as below

SERVER1 192.168.*.* (whatever the ip is)

Then edit /etc/nsswitch.conf and enter

hosts: files[NOTFOUND=continue] dns

This will allow your system to resolve DNS through the /etc/resolv.conf file and if it does not find a system it will go to the DNS server.

Enter the names in /etc/resolv.conf file for only the most accessed servers for better performance.

-Anil

Re: name resolution from DNS server

harry d brown jr — Fri, 07 Apr 2006 11:38:47 GMT

Take a look at this thread: http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=840826

look for my post that included an attachment. The attachment (tar file) allows you to make your HP servers DNS caching servers - which should make your DNS queries very fast.

Note: If you are talking about slow logins using SSH, then you are toast. SSH appears to try IPv6 DNS lookups first, then fails back to IPv4.

Hopefully Rick Jones will pipe in here :-)

live free or die
harry d brown jr

Re: name resolution from DNS server

Bill Hassell — Fri, 07 Apr 2006 16:09:54 GMT

The most common reason for a slow login is that the DNS servers don't work right. They may be just fine for WINS resolution on PCs, but you must first verify that all the DNS servers listed in /etc/resolv.conf actually work for your HP-UX system. Use nslookup's special option to query a specific server:

nslookup some_server dns1.mydomain.com

where some_server is a hostame that should work OK. If it completes very fast, all is well. If it fails, talk to your DNS aadministrators.

The second test (which is likely the problem) is to use nslookup to find your PC's hostname and then find your PC's IP address:

nslookup myPCname
nslookup 12.34.56.78

Many Windows adminstrators fail to provide reverse lookup records. This is an imperative security requirement for all DNS servers. The DNS boxes must be able to resolve hosts and IP addresses both directions. HP-UX tries to validate your PCs IP address and gets no response so it waits for 15-20 seconds.