email and dns
Posted on 2001-07-11
I am back again trying to solve an email/dns problem. I run a mail server on my small lan ,and have a quasi-permanent connection to the internet. This means that although my isp is supposed to be providing 24/7 uptime, their service has these strange 60-90 second blackouts every 15-20 minutes they cannot solve.
This affects me because when someone tries to check their email at the same time one of the blackouts are occuring, it causes the response to be really slow. jlevie pointed out a way to cure the other problem I was having by suggesting I correctly maintain an /etc/hosts file. But with the blackouts, my pop server has a delay because I think that it is trying to do a reverse lookup of itself. Here is a sample tcpdump output. 192.168.1.3 is the machine running qmail. 192.168.1.20 is my machine checking for email. 18.104.22.168 is my isp's dns server.
20:14:41.731133 eth0 < 192.168.1.20.1363 > 192.168.1.3.pop3: . 1:1(0) ack 1 win 17520 (DF)
20:14:41.732146 eth0 > 192.168.1.3.15093 > 22.214.171.124.domain: 61116+ PTR? 126.96.36.199.in-addr.arpa. (42)
20:14:41.748817 eth0 < 188.8.131.52.domain > 192.168.1.3.15093: 61116 NXDomain 0/1/0 (104)
So my basic question is what entry, if any, can I place in my /etc/hosts file that will prevent the reverse lookup? (or give the correct response?) I have tried various combinations to little avail. I would rather not set up a dns server on my lan. I have only 12 nodes and the changes here are very infrequent at best.