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I have a new Wifi router, and for some inane reason, my modem won't allow bridged mode for my ADSL2 connection.

How do I set up my external router, and my current modem/router so that the dedicated router handles all tasks such as DHCP, Access point, port forwarding etc?

The specific questions I have are...

  1. Do I set both devices to be on the same IP range, or have them separate? (e.g one on 192.168.0.1 and the other on 192.168.1.1)
  2. Do I disable DHCP on the modem if it is on a separate range?
  3. How will I set up port forwarding? Is it just a matter of forwarding ports from the modem to the router, and then on to the local location?

Edit: My original modem/router does allow bridge mode for VDSL and Fiber, but just not ADSL2, which is frustrating.

  • Modem/Router: Huawei HG630b
  • Router: D-Link DIR-880L
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    Q: "What is best practice for setting up my external router...?" A: There are no best practices.
    – Mike Pennington
    Commented Dec 26, 2014 at 21:33
  • OK thanks I didn't know about this. I will reword it.
    – square_eyes
    Commented Dec 26, 2014 at 22:42
  • we might be able to improve answers to this question if we knew what model and manufacturer router you have. Could you add that information to the question?
    – Mike Pennington
    Commented Dec 27, 2014 at 11:28
  • It may seem counter productive to my cause but I left this out so the question would be useful to anyone else. I couldn't find much info on the web about what I imagine is a relatively common configuration question. My carrier supplied modem firmware seems to be pretty locked down and relatively uncommon due to my locale.
    – square_eyes
    Commented Dec 28, 2014 at 0:23

1 Answer 1

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Really there is no best practice; the best you can do is choose the lesser evil.

  1. Connect with one subnet, as you describe in your question.
    • If it is connected to one common client subnet, DHCP must kept only on one device
    • Set the default gateway to the ADSL device
    • You must configure all firewall, dst-nat (eg. portmap, service publication), UPnP on ADSL.
    • In this scenario You interconnect LANs of Modem and Router.

But if 1. is sufficient, why do you need a separate router?

  1. Connect your router's WAN port to LAN port of the ADSL device.

    • In this scenario You need 2 subnets: ADSL LAN <-(subnet1)-> WAN Router2 LAN <-(subnet2 real LAN)-> PCs
    • If the ADSL device supports a "DMZ" (map all connection to one internal IP), then you can configure it to IP of Router2's WAN interface. Then you can get inbound connections, and configure dst-nat (eg. portmap, service publication), UPnP on Router2.

  2. Exotic scenario. If ADSL router, support PPPoE passtrough or relay feature, You can enable it, connect WAN of the router to LAN of Modem and configure PPPoE on Router.

    • It possible preferred scenario, because it assign external IP directly to Router, but it use relative rare feature.
    • In this scenario, can be hard to manage adsl modem from LAN
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  • OK thanks for the advice, in scenario 1 above where do I connect, if not WAN of router to LAN of modem? As you mentioned for scenario 2?
    – square_eyes
    Commented Dec 26, 2014 at 22:42
  • I change reply. In 1 scenario You interconnect LANs of Modem and Router.
    – Mikhail Moskalev
    Commented Dec 27, 2014 at 12:51
  • OK thanks for clarifying that. Just so I know, what do I miss out on not having bridge mode? Is there a trade off in speed?
    – square_eyes
    Commented Dec 27, 2014 at 19:12
  • Actually in speed no trade off, except situation where ADSL modem too weak to handle full speed in Router mode. Main trade off in ability to receive inbound connections. It can limit ability to transfer files in IM, use VoIP, make servers (as Web, FTP, VPN, etc...). Third scenario is completely free from this trade off.
    – Mikhail Moskalev
    Commented Dec 27, 2014 at 21:11
  • I use port forwarding, see my question # 3. Can I forward twice? So from modem/router, to router, then from router to local host?
    – square_eyes
    Commented Dec 27, 2014 at 21:22

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