WIFI networking: two routers on the same network

January 13, 2013 5:45 AM

Hi, I am trying to set up a surplus router as a NAS and torrent appliance, to integrate into an existing network. The setup will use two routers, one to provide network and internet to everyone, the other will use TomatoUSB and will be dedicated to torrenting.

Existing setup: A Netcomm all-in-one router which does VOIP, modem, WIFI, routing etc currently does all networking for the house. The household has three Windows PCs, three iPads, two smart phones, one network printer/scanner/fax. The most network intensive thing it ever does is torrent downloads, but VOIP call quality can be an issue sometimes.

I have an ASUS RT-N16 router, which I have flashed to TomatoUSB, which includes built in support for Transmission torrent software. I wish to use this as a dedicated torrent downloading machine, integrated with my existing network.

Flashing TomatoUSB on was fine once I found a compatible build, I installed Transmission QT on my PC and that's working fine too. Everything works.

But it's not set up properly. To get my computer to talk to the Tomato router I need to log in to the Tomato router's WIFI network. When I'm logged in to that WIFI network I can set up the torrents, but I'm disconnected from the rest of the network and can't print. Therefore I've got this awkward arrangement where I have to switch between WIFI networks depending on what I want to do.

Why? Because I can't figure out how to get it working the other way!

So this is less a question about TomatoUSB, more a basic question about network and WIFI setup, router configuration etc.

Currently the Tomato router is wired via its WAN port to one of the LAN ports of the Netcomm router. The Tomato router refuses to let me set it's network IP and subnet ranges the same as the WAN, hence I have two networks that don't talk to each other.

I do not require the Tomato router to do anything wirelessly, I'm happy enough to turn off its WIFI signal and have it communicate only with the network with ethernet cables.

I've heard about "bridging" routers, but admit I'm not knowledgable enough to know how to use it properly. My attempts to muck about with it and figure it out resulted more than once in being locked out of the configuration screen and having to factory reset, so maybe I need expert help!

Of course I have Googled the issue, but everything I have found so far describes setups different to what I want, like bridging Internet to the Tomato router and having it handle the whole network, or using the second router to extend WIFI range.

Also, I want to be able to quickly kill torrents if I have to, so although I could configure it so the Netcomm router bridges its internet connection to the Tomato router which then would handle all the WIFI, this is not the option I would like to go with. I wish for the Netcomm router to continue to handle everything it currently handles, which it does perfectly well, and for the Tomato router to simply join that network and be able to be switched off any time I so wish. Also, the Netcomm is doing a great job where it is, I am not worried about needing to increase the wireless range or anything like that.

Briefly, my questions are as follows:

Do I need two cables, one to the WAN and one to the LAN, or can I set it up so that a single ethernet cable (to either the LAN or WAN ports of the Tomato router) would join the Tomato router to the network? I assume it's possible to use one... how?

I also suspect I should be turning off DHCP and NAT from the Tomato. How do I do that without getting locked out of the device? Both previous times I've played with that I've had to reset to factory settings to get back in.

What LAN and WAN settings on the Tomato router would tell it just to passively join the other network and not try to form its own one?

posted by Mokusatsu to computers & internet (7 answers total)

Yes you absolutely need to turn of DHCP and NAT. You should only have one DHCP-providing device on your network, otherwise they will conflict with each other, this is what's stopping you from setting the Tomato's network and subnet ranges to the same as the WAN. Using NAT creates two separate networks, and could cause issues for any device connecting through it.

A "bridged" router is just an extension of the existing network. If you don't need the Tomato's wireless capabilities, turn these off to simplify things. Connect a LAN port on the Netcomm to the WAN port on the Tomato, then try to find a guide on how to set up the Tomato router in Bridge mode. If you successfully bridge with a router, ALL devices connected to its LAN connections should act as if they were connected directly to the Netcomm.

It's possible that Bridge mode might prevent the torrent software from working. I'd need to do a lot more reading to find that out, but your first job is to get network devices connected to the Tomato picking up IPs and accessing the internet successfully. THEN you can worry about the torrenting.
posted by fearnothing at 6:09 AM on January 13

You just turn off all router funtionality (DHCP especially) on the tomato box and assign it an ip in the range of the first router. Done. You don't need to put in bridge mode. You're just essentially converting it from a switch into a cheap server.
posted by empath at 6:42 AM on January 13

The easy way to turn off DHCP on a router is to just not use the designated special WAN port of that router. Just use one of the other ports.
posted by Obscure Reference at 7:19 AM on January 13

You probably will have to turn off all WAN firewalling on the tomato router. These normally desirable security features probably prevent you from reaching the tomato router over its WAN port from your normal LAN/WLAN.
These security features are needed if the WAN port of the router faces the big bad internet but are not really necessary on your local network.

I am not familiar with the tomato firmware. This option can be worded on the configuration page as either nice and straight forward technical language (turn of firewall on WAN) or it can be phrased as: "allow management over WAN port".

An additional obstacle four you could be that the tomato router only sucks torrents via the WAN port and only allows you to administrate the torrenting over one of its LAN ports. If this is the case you can still work around this problem by manually giving your desktop computer two IP adresses:
- Switch off the dhcp server on the tomato router as mentioned by everybody else because you do not want to have two dhcp servers on your LAN.
- Give the tomator router an adress of its own, different from your local network since the tomato router is already talking to your local network over its WAN port
- Connect the tomato router LAN port to an additional LAN port on your normal router. It is now connected to your LAN twice but since dhcp is off it does not disturb your normal LAN, you essentially now have to different networks on the same wire. (If you setup the tomatao WLAN to the same network name and encryption you can probably also use the tomato WLAN to extend your current WLAN as a bonus without any further configuration)
- In the Windows/MAC/Linux networking setup of your desktop computer you can specify an additional IP adress for your computer's LAN (often called an alias). Choose this IP adress from the tomato router's LAN IP range, do not enter the gateway part. Your computer is now part of two networks over the same wire.

Example: Your desktop computer gets an IP of 192.168.1.10 via dhcp from your normal router (IP 192.168.1.1) . It also gets DNS (192.168.1.1) and gateway(again 192.168.1.1) information from that router via dhcp.
In addition you have given your desktop computer the IP 192.168.2.10. This should be the IP range of the tomato router's LAN. The tomator router should have the IP 192.168.2.1 on this network.
If you want to control your torrents you point your web browser to 192.168.2.1 and talk with the tomato router. Other IP adresses will be routet the normal way since that is where your gateway points to.

I hope this makes sense to you. It's quite hard for me to give you a short explanation. There are so many branching possibilities how you could configure your setup and how the tomato firmware might behave.

If the tomato router allows torrenting and the administration of the torrenting both on the LAN port, all of the above becomes uneccesary. As Obscure Reference points out, just connect one of the LAN ports of the tomato router to one of the LAN ports of your normal router.Turn off dhcp on the tomato router. Since the tomato router will probably not be willing to get an IP address over dhcp from your normal router for its LAN port, you will have to configure that adress manually with the address of your normal router for DNS and gateway. (And the WLAN extension a mentioned above will be possible, too)
posted by mmkhd at 7:36 AM on January 13

> The easy way to turn off DHCP on a router is to just not use the designated special WAN port of that router. Just use one of the other ports.

This isn't true. DHCP is used to assign addresses to devices connected to the LAN side of the router, so if you have the DHCP server enabled, and a device connected to a LAN port of the router makes a DHCP request, it will assign an address. Even worse, if you have two DHCP servers that are connected to the same network, both will assign an address, and the device will accept whichever one it happens to receive first. Depending on configuration, it's possible that the two routers may assign the same address to two different devices, which works about as well as you'd expect.

I think mmkhd has the solution. Start with the last paragraph, and only move to more complicated stuff if that doesn't work. If you configure your tomato router to have a Static IP that's in the same subnet as the netcomm router, but outside the DHCP range (so that it won't also hand that address out to another device), you will still be able to access it after you turn off DHCP/enable bridge mode.
posted by yuwtze at 11:16 AM on January 13

Well, I've established that plugging the ethernet cable into the LAN port doesn't work. It simply didn't get Internet.
posted by Mokusatsu at 11:21 AM on January 13

I don't know about Tomato, but I have something like this set up with DD-WRT. I had to set up something called "Client Bridge" mode. It requires that you establish a second SSID, I think with the same password as the initial network, and then the "child" router just joins the parent. You do have to turn off DHCP on the "child", and it forwards all client requests through to the parent who assigns addresses from its main DHCPD pool.

The one drawback to this setup is that you essentially halve your bandwidth between the two routers. I can't quite recall the reason, but it seemed logical to me when I read it.

For that reason, if I was going to be doing what you describe, I'd make the box closest to the outgoing WAN connnection the torrent box and have all local users connect to the client. That way all your torrent traffic will be making the most efficient use of the available bandwidth and not having to use up internal bandwith on an extra hop between routers.
posted by hwestiii at 5:24 PM on January 13