Multi-homed box acting as a DNS and Mail Server.

[Gareth Bromley]

Melvin Toy wrote:

> I'm a newbie experimenting with bind and sundial.  I have a box at home
> with 2 nics(one real static IP and other private 172.16.x.x) running
> Redhat 6.1 with a cable modem.  I have another box (box A) running RH6.1
> at home with a private IP and one (box B) at work running solaris 2.7
> with a real IP. I temporary add my DNS server as the name server for box
> B. I can email from my dns/mail server and it also relays box A messages
> to box B and masquerades correctly.  However when I reply, my mail
> bounces.  I tried to telnet to port 25 by FQDN of the dns/mail server
> from box b.  I notice it was trying to telnet to the private IP instead
> of the real one.  When I do an nslookup by name both IPs are return.
> How do I get box B to use the real IP every time.  I know I going to
> have more issues with sendmail but I'm trying to eliminate all
> non-sendmail problems first. My first thought is to create a separate
> record for the internal nic. Is that legitimate and typical solution?
> How will that will affect sendmail?

Creating an internal domain would be best, or wait for Bind 9 which will
include more advanced support for views, which would display valid Internet
addresses to Internet hosts and Intranet addresses to Intranet hosts from
the same conf files I think. (You can do this already by using an ISP to
host your Internet side, and you to host your Intranet side.

For sendmail you use .cw files, or MASQUERADE statements to force sendmail
to accept mail for many hosts at your gateway e.g.
domain.com
intra.domain.com
host.domain.com

See: MASQUERADE-DOMAIN-FILE, MASQUERADE-DOMAIN in the m4 macros
(http://www.sendmail.org)

--Gareth