Trouble configuring Windows Server Enterprise as a NAT router

Giganews Newsgroups
Subject: Trouble configuring Windows Server Enterprise as a NAT router
Posted by:  Zenexer (Zenex…
Date: Sun, 12 Apr 2009

I recently upgraded my home server to Windows Server 2008 Enterprise R2 Beta.
As I was setting it up, I got the bright idea to replace my router with the
server.  So I got to work installing a second NIC, disabling DHCP/DNS on my
router, etc.  All went well--until I tested it.  I cannot, for the life of
me, get NAT to work.  I have two NICs in my server: one for LAN, another for
WAN.  The WAN NIC is connected via ethernet to a standard broadband modem and
works fine; I can successfully access the internet from the server.  The LAN
NIC is connected (also via ethernet) to a wireless and wired router.  The
router was already configured to behave as a standard switch, as I had
previously used the modem as the DHCP/DNS server (it's one of those
modem-router combos--can't complain, it was free).  DHCP is a go: anything
that connected wirelessly to the network gets a proper IP, with the server
marked as the Def.GW and DNS server.  Now, here's where the problems
start--that's the only thing that works.  I can ping the server just fine,
but DNS requests fail (they work locally on the server, which is configured
to use as the primary DNS server with as backup).
External requests result in a "host unreachable" error.  It seems as though
the switch doesn't understand that it's supposed to forward traffic directed
outside the subnet to the server (, even though RIP-2B is enabled
on both the server and the router.  I haven't seen any suspicious log entries
or such.  Windows Firewall is 100% disabled.  As far as I can tell, RRAS,
DHCP, and DNS are all configured properly, though the results seem to speak
otherwise.  I have to admit, networking at the hardware level is not my area
of expertise; this is a bit different than working with winsock.  After
programming for years, I never thought anything besides a segfault could
frustrate me on a computer--clearly I was wrong.  I don't know how you
network techies do it.  Does anyone have any tips?  I've worked with Server
2003 quite a bit in the past, so feel free to give directions in terms of
another (similar) OS; I should be able to figure it out.