Accessing Modem from LAN when in bridging mode

[mbaker]

Hi everyone,

I'm looking to set up a LAN at my parents house using the following gear:-

• Netgear D200 ADSL Modem Router
• ASUS RT-AC66U_B1 Router running latest version of Merlin

The key requirements, over and above basic access to the internet, are to:-

1. Run a OpenVPN server and DDNS service from the ASUS router (so that I can connect to this router / LAN from over the internet)
2. Run the DHCP server running from the ASUS router (so that all LAN network activity is logged in one single place)
3. Be able to access the Netgear control panel, when connected to the ASUS router LAN (in order to help diagnose any ADSL connectivity / speed issues)

For 1 and 2, my plan would simply be

• Set up the Netgear D200 to Bridge Mode, thus making it a simple modem
• Connect the Netgear LAN port to the WAN port of the ASUS Router.
• Set up the ASUS in Router mode, with DHCP server, OpenVPN server, and DDNS service

However in this configuration, I don't think I have access the Netgear control panel from within the LAN.

I'm wondering what the simplest, most reliable way is to achieve all 3 requirements above?

I had considered running the Netgear D200 in modem router mode, with DHCP turned off, and placed on the same LAN as the ASUS by connecting the Netgear LAN port to the ASUS LAN port. But if I do this, won't I run into routing conflicts and with the DDNS set up?

I'm doing the research ahead of time because I will have a very tiny limited time window to experiment and get this set up when I'll have actual physical access to the Netgear D200 at my parent's house (I do however have the ASUS router with me currently). Hence, the reason for the asking for everyone's help - thanks!

 

[ColinTaylor]

However in this configuration, I don't think I have access the Netgear control panel from within the LAN.

Try it before you go down more convoluted paths. I know some people have problems accessing their cable modem in bridge mode (particularly in the USA), but I've never had an issue accessing my cable modem. It just works. YMMV.

The manual for the DM200 says:

IMPORTANT:
After you disable the modem’s routing features and the modem functions as
a DSL modem only, you can access the modem only through a fixed IP address,
which is 192.168.5.1. Therefore, make sure that IP address 192.168.5.1 is not
assigned to another device on your network.

So just make sure your LAN is not using the 192.168.5.x subnet.

 

[mbaker]

Thanks for the fantastic pointers on this - I didn't spot that line in the manual. As mentioned, I only have a small window of time to try things out when I'm at my parent's house hence, the slight pre-emptive question, but your pointer above gives me confidence on this.

One question though, I'm setting the ASUS Router and the DHCP pool to be on 192.168.10.x as a way to ensure when I connect to the OpenVPN server from an outside 192.168.1.x network, there are no clashes with the ASUS AC66U_B1 LAN (I had issues with this before when I had a Raspberry Pi OpenVPN server running inside my parent's house on an old router). Do you think I will still be able to access 192.168.5.1 from via the OpenVPN connection from outside i.e. accessing the ASUS 192.168.10.x network from a 192.168.1.x network via the ASUS OpenVPN server, in order to log into 192.168.5.1? Apologies, I'm hitting the limits of my networking knowledge and hence, don't fully understand the implications of all the above.

 

[ColinTaylor]

As mentioned, I only have a small window of time to try things out when I'm at my parent's house hence, the slight pre-emptive question, but your pointer above gives me confidence on this.

It is wise to try and cover every eventuality when you only have a limited window. If it doesn't work "out of the box" then I don't know what to suggest as it's not a problem that I've personally encountered. There are some guides on the wiki about accessing modems.

The simple approach tells you to temporarily change your WAN IP address to be on the same subnet as the modem's interface. This approach won't work for you because it disconnects the link to the internet, which your VPN is coming through . Another technique involves creating a second virtual WAN interface, in your case on the 192.168.5.x network. There's an example here. I'd guess you'd need to change 192.168.100.2 to 192.168.5.2.

Do you think I will still be able to access 192.168.5.1 from via the OpenVPN connection from outside i.e. accessing the ASUS 192.168.10.x network from a 192.168.1.x network via the ASUS OpenVPN server, in order to log into 192.168.5.1?

This is something that you'll just have to try it and see. You must have the VPN client and server setup so that ALL of the client's traffic goes through the VPN. As far as the VPN client is concerned 192.168.5.1 is "on the internet somewhere" not on the remote LAN. So the OpenVPN server must have "Direct clients to redirect Internet traffic" set to yes.

 

[coxhaus]

Using a typical cable modem in bridged modem you access the modem web page using 192.168.100.1. In bridge mode the modem is just passing info to the router. There are no router controls available in bridge mode.

 

[mbaker]

Try it before you go down more convoluted paths. I know some people have problems accessing their cable modem in bridge mode (particularly in the USA), but I've never had an issue accessing my cable modem. It just works. YMMV.

The manual for the DM200 says:
So just make sure your LAN is not using the 192.168.5.x subnet.

Am onsite now sorting this out and I can report that switching the D200 to Modem (Bridge Mode) only does work. The Modem LAN port is connected to the ASUS RT-AC66U_B1 Router WAN port. I had to enter the ISP ADSL connection details in the ASUS WAN config page. My test computer is now connected to the ASUS router with a 192.168.10.x address.

However, unlike how the manual states, I cannot reach the modem if I try 192.168.5.1. It just times out.

Anyone have any other suggestions how I can reach the modem other than plugging my laptop into the LAN cable?

 

[ColinTaylor]

Anyone have any other suggestions how I can reach the modem other than plugging my laptop into the LAN cable?

Can you clarify. Are you saying that you can access the modem if you connect to the LAN with an Ethernet cable, but you can't when connected remotely via VPN?

 

[ColinTaylor]

Looking at this reply it looks like you'd have to use the solution I linked to in post #2. Whether that will actually work or not...

 

[mbaker]

Can you clarify. Are you saying that you can access the modem if you connect to the LAN with an Ethernet cable, but you can't when connected remotely via VPN?

All this is whilst connected locally - no VPN in the picture at the moment. So simply wifi connection to the Asus router, which is in turn connected to the Netgear modem (via ASUS WAN port).

 

[ColinTaylor]

All this is whilst connected locally - no VPN in the picture at the moment. So simply wifi connection to the Asus router, which is in turn connected to the Netgear modem (via ASUS WAN port).

I think you need to ignore the Asus for the moment and confirm whether or not the modem is accessible at all at 192.168.5.1. So configure your laptop's Ethernet interface with a static IP address (say 192.168.5.10) and plug it straight into your bridged modem. If you can't get that to work there's no point going any further. Check different Ethernet sockets on the modem because it's quite likely that only one of them can be used.

 

[coxhaus]

Did you try 192.168.100.1? All the modems I had have been accessed by the 100 network. You need to make sure routing is going out for the 100 network. As long as you have 0.0.0.0 0.0.0.0 going outside and the 100 network is not defined on your LAN it should work.

 

[Turgut Kalfaoglu]

Was there any solution to this? I set my N17U to bridge mode (NOT media bridge mode), and the CISCO router behind is it doing the PPPoE.. No problems.. But despite plugging in a LAN cable to another port of the N17U, and manually trying many IPs and routings, I can't reach the modem.. I tried 192.168.x.0 C class subnets where x was 0,1,2,5,10,100.. no luck.
I just wanted to query things like CRC count, link speeds, etc..

 

[Turgut Kalfaoglu]

GOT IT -- simply plug an ethernet cable to the 3rd port on the back of the ASUS DSL-N17U modem.. It even has a DHCP still running in Bridge mode!