[ILUG] IP Masquerading

[Tom Cooper]

Hi all,

If I have a machine acting as a router, one interface on the
public network, one interface on a private network and
DNS lives on the public network, and I have an ipchains
setting as follows:

ipchains -P forward -j ACCEPT
ipchains -I forward -s 192.168.0.0/24 -d 0/0 -i eth1 -j MASQ

Now if I set up the mail server (POP and SMTP) as the public interface,
say mail.somedomain.co.za - ip address 196.1.2.3, surely the ip adresses

on the private network will resolve t the public ip address, even if the

internal
machines talk to the public ip address directly, i.e. 192.168.0.1 looks
up
mail on port 110 on 196.1.2.3, it will resolve to 196.1.2.3. Now if
196.1.2.3 is
set up as a valid DNS entry and the reverse DNS is set up properly, the
system
won't hang, trying to hook a name to the ip address.

This setup has been working on my network for months and this week al of

a
sudden, the private IP addresses hang when connecting to the mail
server.

I did not change DNS, masquerading or anything to do with routing
lately.

Any ideas?

Tom