Does your external NIC on the server have a public ip / connected straight to a router or does it go in to another router?
What is happening is (if your setup is as I expect above)-
Client looks up IP and sees that it is outside of your local network
Client goes to its default gateway (your Windows 2008 Box) and says the ip.
Windows 2008 says not here, looks up the default gateway and forwards the request to your router.
Router says, that IP is mine, but then hangs and times out!
See if your router supports NAT Loop-back. Basically, NAT inside Windows 2008 is working, but the DNS IP is your public one and RRAS does not realise that it is it's own IP, and therefore doing its job and routing to its external network.
If you say the make/model of your router, I can help you further (if it supports it)
Another way that can get awkward is to install your own local DNS server on the Windows 2008 box and refer all clients to it (make it forward queries to your current DNS servers) and force in a zone for each of your domains that have your internal records.
... Or if you only have a handful of machines and the router does not support NAT Loop-back, and you understandably do not want to buy new hardware, insert your record in to the machines' host file. This is a surprisingly efficent technique and providing you have admin access to shares, you can script this VERY easily by just placing it in a directory then doing
copy hosts \\\computer_name\c$\windows\system32\drivers\etc\hosts
And all done without a reboot!
Of course, the prefrence is just to enable NAT Loopback!
Anyway, hope I helped and this was the issue... Dreading your reply of "I only have a modem and the server is using a external ip in it's config!!"
I think I have this exact same problem on a new 2008 R2 cluster with an equallogic, what is the solution? I have a microsoft case and they're pointing me to weak/strong host but it is not helping.
Here is solution for anything with broadcom NICs (and maybe others):
http://support.microsoft.com/default.aspx?scid=kb;EN-US;951037
You must disable rss/chimney/netdma. Resolved my problems immediately, after dell/ms support calls!
Best Answer
Thanks for the help guys. Apparently the network drivers Dell provided for the R710 needed to be installed without a network cable plugged into them. For some reason the driver installs, restarts the port, and then finishes the installation. So, unless in the split second you disabled the port, it attempted to allocate an IP from DHCP and then canceled. Thereby botching the driver install. The is for Broadcom drivers for Dell PowerEdge R710's.