I want to figureout how to use a public IP address (ISP provided) behind the modem/router.

I'm replacing an aging modem with a NEW one, which is an actiontec GT724R modem. Its manual is Here

This is how I want the setup to look like

                        IP Cop Server                            GT724R Modem
                          |        |                              |       | 
    GREEN (internal)      |        |RED (outside network)         |       | WAN IP
     ---------------------|        |------------------------------|       |------------                                

There's an IPCop Server sitting right behind the GT724R with 2 Nics. is internal network (GREEN) and (RED) will be the public one. and are ISP provided Static IPs.

The IP COP svr is already configured this way and has a lot of setup work done already using, so hence I want to continue to use the public address.

The old modem was in bridged mode and the new one (GT724R) is also configured to run in a similar style, which is "RFC 1483 via Static IP" Encapsulation is "RFC 1483 bridged"

Thanks A


If the new modem is indeed running in bridge mode as well, then the second/new IP should not be tied to the modem at all. It would be on the same plane as your IP Cop server/firewall. In fact, you may even be able to configure IP Cop to manage the second IP as well.

  • Appreciate the response, but I'm not clear about what you mean. So dont tie any IP address with the modem? Aug 5 '11 at 22:45
  • 1
    If the modem is truly in bridge mode, it will not utilize the routable Internet IP. It may have a management IP, but it may not "reveal" that unless it is in maintenance mode (e.g. unable to connect to the ISP network). Is this a DSL or cable modem?
    – user48838
    Aug 5 '11 at 22:55
  • Awesome that helped a lot. I changed the mode to a "RFC 1483 transparent Bridging" mode, which doesnt need any static ip. The earlier mode I was using needed a static IP. Now the modem runs as truely bridged i guess and everything is working the way I wanted it. Its funny how I completely overlooked it earlier. This is a DSL modem btw. thanks for your help. But now I've lost access to the modem....need to figureout how to run it in maintenance mode....but thats a different question i guess Aug 5 '11 at 23:14
  • You don't really need access to the modem, but you can try to disconnect the ISP/WAN end and then try grabbing a DHCP lease from its LAN end - you may need to power cycle the unit while in such an arrangement.
    – user48838
    Aug 5 '11 at 23:19

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