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hux2000's avatar
hux2000
Guide
Jan 21, 2021

Unable to get port forwarding to work on R7800

I can't get port forwarding to work at all on my R7800. Here's what I'm doing:

 

- 'Advanced' tab -> 'Advanced Setup' -> 'Port Forwarding/Port Triggering'

- From the 'Service Name' drop-down, select 'HTTP'

- Enter the IP of the destination server

- Click '+ Add' button and the service appears successfully in the port forwarding list

- Start web service on destination server (for testing, the firewall on this server is disabled)

- Confirm web service is reachable by connecting to its default web page from another system on the LAN

- Attempt to connect from a system on the WAN side by doing 'telnet [public IP] 80': no response

- Attempt to do the same from a system on the LAN: no response

 

I've tried this with several different port, using TCP, UDP and both, but nothing gets forwarded.

 

My network is pretty simple:

 

Comcast modem -> R7800 -> wired and wireless clients

 

Any ideas? Something to do with the modem, maybe?

4 Replies

  • > Comcast modem -> [...]

     

       Not a very detailed description of that device.  Has it a maker and
    model number?  Is it actually a (simple) modem (good), or is it a
    modem+router (bad)?

     

    > - Attempt to connect from a system on the WAN side by doing 'telnet
    > [public IP] 80': no response

     

       What is "[public IP]"?  If you're worried about revealing secrets,

    then the top half of the address, "a.b" out of "a.b.c.d", would satisfy
    most of my curiosity.  Or, plug that address into the form at:
    https://whois.arin.net/ , and see if it is a public or private address.

     

       What's the IP address of the WAN/Internet interface on the R7800
    (ADVANCED > ADVANCED Home : Internet Port : Internet IP Address)?  Same
    or different?

     

       For the usual problems with port forwarding, see:

     

          https://community.netgear.com/t5/x/x/m-p/1859106

     

       I'd worry about "1".  You seem to have covered the others.

    • hux2000's avatar
      hux2000
      Guide

      Thanks for the reply! Answers to your questions below...

       

      "Has it a maker and model number?"

       

      Arris TG862

       

      "Is it actually a (simple) modem (good), or is it a modem+router (bad)?"

       

      It's a modem + router. I thought I'd disabled the router part but now when I try to login to check, it doesn't let me. (I'm waiting on Comcast to do a password reset on it.)

       

      The WAN-side IP associated with my Comcast account, i.e. 24.21.x.x (the output of https://icanhazip.com, for example).

       

      "What's the IP address of the WAN/Internet interface on the R7800?"

       

      10.0.0.6 - it's getting that from the modem.

       

      "I'd worry about "1"."

       

      Yeah, I think you're right: looks like 24.21.x.x is the modem's WAN address and the R7800 doesn't know about that. (Because why would it?) So I guess I really need to get into that modem and set port forwarding there. Or else (hopefully) find a setting that'll just make it pass everything through unchanged.

      • antinode's avatar
        antinode
        Guru

        > 10.0.0.6 - it's getting that from the modem.

         

           There's your problem.  (That's why it's "1" in the list.)

         

        > [...] So I guess I really need to get into that modem[+router] and set
        > port forwarding there. Or else (hopefully) find a setting that'll just
        > make it pass everything through unchanged.

         

           Yup.  If the TG862 has a modem-only ("bridge") mode, then you could
        use it with the R7800 acting as your (only) router.  Otherwise, with the
        TG862 in modem+router mode, _it_ could do the port forwarding, and the
        R7800 could be configured as a wireless access point.  (It's in the
        R7800 User Manual.)

         

           You might have a chance with the TG862 in modem+router mode, and the
        R7800 acting as its DMZ server, but no bets.