[ale] Postfix message router with dnscache

[Bryan Rapp]

I'm having difficulty setting up dnscache to run on a Postfix message router sitting in front of an MS Exchange server.  All I really want to do is cut down on DNS queries when sending mail.  The instructions for dnscache seem quite straightforward but it still is not working correctly; I'm still seeing ';; connection timed out; no servers could be reached'.

I'm currently using RH7.3, Postfix-1.1.11, daemontools-0.76, and djbdns-1.05.  My server has two NICs with the following configuration:

eth0 (facing the Internet with static NAT)
IP: 192.168.13.102


eth1 (facing the internal net)
IP: 192.168.13.101


BIND is currently not installed, and I set up dnscache with the following commands:
#dnscache-conf dnscache dnslog /etc/dnscache 127.0.0.1
#ln -s /etc/dnscache /service


With my ISP DNS address still in resolv.conf, I tested with:
$host theonion.com
theonion.com has address 66.216.104.235


Then tested with the local cache:
$host theonion.com 127.0.0.1
;; connection timed out; no servers could be reached


I've also tried testing the setup using the external address of the mail server with the same result.  


Looking at /etc/dnscache/log/main/current for this query shows:
@400000003daf0c2d37d2a44c query 6 7f000001:8001:eb2f 1 theonion.com.
@400000003daf0c2d37d2bfa4 tx 0 1 theonion.com. . c00505f1 c620400c c021040c c0702404 ca0c1b21 8009006b 80080a5a c6290004 c1000e81 c0249411 803f0235 c0cbe60a c629000a

Also, looking at the external mail interface from my firewall log shows that the mail server is contacting the root name servers in a continual process to achieve name resolution.

Not quite sure what is going on here and I would appreciate any suggestions or tips on setting up and configuring dnscache for this environment.

Thanks,


Bryan Rapp
GeoFields, Inc.
brapp at geofields.com