I recently installed Win2K3 Standard as a PDC, IIS 6 and RRAS.  This
is the only server on the network.  When I first boot the computer
everything works fine, you can see the web pages from the internet
(both ASP and HTML pages) and I can VPN in to the server from other
computers on the internet and use whatever network resources I need. 
After a few hours the server seems to stop responding to any requests
that don?t originate from the local network.  If you try to pull up a
web page from the internet you get a DNS error, that same page pulled
up from a computer on the network works just fine.  It doesn?t matter
if the page is ASP or HTML.  There are no errors in any of the logs
that I can find and I have to restart the computer to get it working
again.  This is frustrating to say the least.  At one point today I
VPN?d in and left the connection open.  After about 3-4 hours the VPN
connection was still open and working but the IIS had quit responding.
 As soon as I disconnected from VPN I couldn?t get back in.  As soon
as the server was restarted it began working again.  The problems have
been limited to just the server, the mail server and an application
server (running on a different computer and a different port) both
work fine through all this.  I?ve been digging though newsgroups and
MSDN articles but nothing so far has worked.

We had a very similar problem on our network.  Our Intranet server
(which ran IIS) would stop serving web requests daily.  It turned out
to be a DNS issue (you even said you were getting a DNS error).  Our
IIS server was also set up to be a secondary DNS server.  It pointed
to our primary DNS server which then forwarded any requests it
couldn't resolve to our DNS server outside the network.

Check your DNS structure.  Are you using Active Directory?  If so, you
have to have a DNS server on your network.  Is you DNS server Active
Directory integrated or just a primary zone server?  Do you have more
than one DNS server?  The problem for us is that our primary DNS
server was not allowing dynamic updates and this was causing our
secondary server to stop responding.

I hope this puts you on the right track.  If you can give me some more
information on your DNS structure, we can see if this is the problem.

jT

I'm using Active Directory and DNS is running on the server, its also
setup to allow updates and forwards DNS requests to the router. (the
router is connected to a cable modem)  This is a small network and the
the DNS server is basically there because it's required.  DHCP lists
it as the first DNS server and the router is listed as the second DNS
server.  It appears to be working fine, if someone on the network uses
http://<machinename> the website works fine and always has.  If
someone from the internet uses http://www.mydomain.com it depends on
how long it's been since the server was rebooted.  After that 3-4
hours no one from the internet can get to any of the web sites and VPN
stops responding as well.

Last night I discovered that if I stop and re-start RRAS then IIS and
VPN start working again...this is MUCH better than rebooting the
server.  I'm starting to look into RRAS and see if I have something
messed up in there.

Thanks for the info.