Disable revers IP lookup

[Gumeni]

I have the following problem:
-When I want to get my email for the first time in a morning my authentication process to mail server (HP-UX 11.00) is during about 5 minutes (too long). After that all authentication processes are very fast.
I suspect an revers IP lookup process that can delay my connections to mail server.
Can I disable revers IP lookup on server ?

[Rhonda Thorne]

You have not given enough info to determine that it is a revers lookup issue. However, if you have DNS setup for chache, you may have a DNS server issue, but after the call fails the server then goes to the secondary ( the 5 minutes delay/timeout) then the cache is updated and resolution is faster because clients are going to DNS cache rather than going back to the DNS server.

You need to verify that the DNS server is working from more than one client, determine is it just one client that has to wait or is it many, verify that /etc/resolv.conf is pointing to correct server and that named is running on the DNS server

Good luck

[Rick Garland]

The reverse nslookup comes from the PTR record in DNS. Are these records looking OK?

[rick jones]

One cannot disable reverse IP lookups on a server-wide basis. They can only be disabled on an application by application basis. So, while the proper thing to do has already been discussed - making sure your DNS is setup properly, with PTR records and such, if you get really stuck, you might peruse the documentation for your mail server software and see if it has a "no DNS" switch like most web servers do.

[Tim Malnati]

I'm having trouble with the idea that DNS is the cause of your problem. Even with everything in the DNS chain timing out I just can't see anything that cause DNS to even approach a 5 minute delay. There is obviously something impacting the authentication process, but I doubt that it's DNS in of itself.

Off the top of my head I would be more inclined to look at NIS or NFS mounts as a more probable cause. NIS could be any number of update related issues. NFS mounts can be particularly problematic if the authentication process causes a users quotas to be checked and a mount is down.

[rick jones]

one could try a tusc system call trace of the mail server to see what it is doing for those five minutes. there are tusc options to include timestamps which would be a good idea. DNS requests using typical UDP would be a series of sendto() calls.

tusc can be found at ftp://ftp.cup.hp.com/dist/networking/misc/