Configuration of a web server with two NICs


I have this situation:

I have one web server, with Windows 2008 server hosting my web site. This server is connected with one NIC to a ADSL router and with the other to LAN (with firewall).

On the 'external' NIC I have this IP vaules:

DNS Server:

On the 'internal' NIC (the one that leads to a supposed LAN trhough a firewall) :

DNS Server:

This configuration works properly to serve website to external petitions almost 90% of the time. But sometimes the server doesn't do his job: clients can't access to IIS and I have to disable 'internal' connection. This solves the problem, because instantly website is served again.

I undestand that there is some missconfiguration with the routing, but I can't find the error. Can anyone tell me some clues?

Thanks a lot and kind regards.
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add static routes in the machine

the machine needs a route to forwards packets to internal client without ambiguity do

route add mask metric 1 -p

and to force the machine sending all trafic not destined to you r internal network do

route add mask metric 1 -p

its necessary to make these routes persistante with  -p .

also change the card binding  in Network and sharing Center > change adapter Settings > in the menu , Advanced setting > advanced .

remove the gateway from the Internal nic

in the other hand consider removing the second nic and working with One nic . it will be easier and cleaner architecture .
Aaron TomoskySD-WAN SimplifiedCommented:
You internal has the ip of the external as it's gateway? This is not how I would normally set this up. I don't see the point of even having two nics with this config. What exactly are you trying to accomplish here? Any reason not to just have one nic on the LAN and forward port 80 to it?
Darius GhassemCommented:
Go to your network card bindings make sure your external NIC is listed first.

You shouldn't need to have the DNS server in internal network configuration
You need to remove the gateway from the internal NIC and add static routes to the inside network as necessary. You didn't include subnet masks, but it also looks like the router on the internal NIC may not be on the same IP subnet as your NIC interface, depending on you subnet mask and whether or not you correctly posted the IP addresses.  

To add a static route under Windows, look at "route /?" From command prompt.
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