NAT Loopback

So i have done some more testing.

If i type in my web address something.com with port forwarding turned on. external devices can access but nothing internal. But oddly if i turn port forwarding off, obiously nothing from the out side comes in but on an internal device it is actualy giving me my comcast modem interface.

I have found a temperary work around, by adding to my desktop computer's hosts file. doing this i am able to access the webservers with no problems. I realisticaly cant do this to every device on my network and would also rather not setup a localdns server.

 Does this confirm that i am haveing NAT loopback isues that are being caused by the modem itself?

And anyone have a good solution?

Hi Tallguy64 and welcome to the business forums. 

I can help with what you're looking for in the gateway. You're most likely looking to set up Passthrough Mode. 

Passthrough Mode describes a gateway which has its LAN DHCP and Firewall manually disabled through the user interface. This allows traffic to passthrough the modem to a routing device and can be used if the customer has a Static IP address. This is not true Bridge Mode and does not convert the gateway to a basic cable modem. This mode allows most of the routing capabilities of the gateway to remain intact. 

Please let me know how this works for you. 

Could you elaborate on how to set this up.

Disableing the fire wall is simple enough, and taking the DHCP offline i unederstand but from there what do i need to change?

Also by taking the lan dhcp offline would that mean that i would lose the wireless functionality in the comcast unit? I had planed on using the seperate wireless network for the home automation software i use to seperate that from my other computers and server. Not a deal breaker as i can setup my main router to have a guest wifi so that it is on its own network.

As of right now I setup a local dns server and that has seemed to fix the problem for now. My concern is that i might run into problems as the next thing i am setting up is the mail server and i am wondering if i will run into problems with the webserver doing loop back to the email server, but we will see.

Thank you for the kind answer, i have been crash coarsing myself though network administration LOL. and i am starting to understand how it is working, but still not completely there yet.

The LAN DCHP can be found under Connection > Local IP Network.

You're also correct with the wireless functions. Once disabling the DHCP, you would lose your wireless capabilities. Using your own router is definitely recommended. I am able to assist with configuring your gateway. However, please do keep in mind that I am not able to help set up your private network as this would be beyond the Comcast Business demarcation. Please let me know if you need anything additional. 

Ok thanks, i think i should be fine for now but we will see.

I thinking i understand how to set the gateway that should be easy enough. I was just wondering with taking down the DHCP i would then set the router to a static IP, but would that IP be and internal ip 10.1.10.5 for example or would i set the router to have the ip of the static ip address?

Going out on a limb, if i were to get a second static ip so that i could run two seperate networks how would i set one ip to go to one router and one to go to the other? is this where the nat 1 to 1 comes into play?

Taking down the DHCP means you would have to manually assign the LAN IP to your device. I would recommend reaching out to a networking IT team for those questions. Please let me know if you need anything.