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Linking Routers via Wifi

Link your routers together

Wireless Interconnection of Routers

It is possible to link one router to another by using the two router's Wifi. This gets rid of the need to connect the routers using Ethernet cable, which can be a problem in mant situations. Linking by Wifi is very quick to and is much cheaper than cable.

If you only wish to have Internet supplied to one router by another router then you would use the Wifi Hotspot Manager to achieve this. Instead, we will be looking at a Wireless Distribution System which will join the two routers into a single network so that devices on one router can access devices on the other. Wifi roaming is also supported with devices switching from router to router when the signal strength is low.

Prerequisites

Setting up a Wireless Distribution System ( WDS ) requires that both routers use the same type of Wifi chipset and both must be using Lede or OpenWrt based firmware like ROOter. This system has been tested on routers using the Atheros wifi chipset but other chipsets may also work. It does not work with the Broadcom Wifi chipset.

Link Speed

The speed at which the wifi link operates depends on two things, the spectrum width of the wifi signal and the number of access points on the link. The spectrum width of the wifi on a ROOter can be either 20Mhz or 40Mhz for 2.4Ghz radios and 20Mhz, 40Mhz or 80Mhz for 5Ghz ones. WiFi has a system spectral efficiency of 2.44 bits/Hz, so 20MHz gives (at most) 48.8Mbps while 40MHz gives 97.6Mbps and 80Ghz has a maximum of 195.2Mbps..

You will probably never see speeds that match the theoretical maximum but speeds of 88Mbs can be reached when using a 40Mhz wide wifi channel. This means that the speed of the link between the two routers will never exceed 88Mbs and, in fact, may be slower.

If you wish to allow a wifi access point on the routers at each end of the wifi link then the speed of the link will be halved, giving you a maximum speed of 44Mbs for the link.

See Increase the Bandwidth of Your Wifi for details on how to set the routers to their maximum wifi bandwidth.

Setting It Up

This is how a typical Wireless Distribution System will look.

Since the two networks are joined using this type of wifi link, the routers must have different IP Addresses, as indicated in the graphic above. And both the Master and Client Routers need to have some changes made to them in order to set up the WDS wifi link.

The Master router is the router that the other router connects to when forming the link. It has the least amount of changes made to it and is usually the router with the Internet connection. However, either router can supply Internet to the network.

The Client router has more changes made to it as it does the connection to the Master router. There is no other difference between Master and Client routers except for the fact that the Client connects to the Master.

Changes to the Master Router

Plug in the Master Router to your computer using an Ethernet cable. Don't attempt these changes using the wifi, since you may loose the connection at some point.

Use the web interface to go to the Network menu and the Wifi submenu and click on the Edit button for the wifi interface you will be using.

Change the Mode to Access Point (WDS) and make sure the Network is set to Lan. Click on Save & Apply.

If the Master Router is supplying Internet to the network then you are finished. If the Client Router will be supplying the Internet then one more change needs to be made to the Master Router.

Use the web interface to go to the Network menu and the Interfaces submenu and click on the Edit button for the Lan interface.

Enter the IP Address of the Client Router in the IPv4 Gateway box. Also enter the IP Address of a DNS Server in the Use Custom DNS Servers box. Shown is the IP Address of Google but you can substitute any DNS Server here.

Click on Save & Apply.

Changes to the Client Router

Plug in the Client Router to your computer using an Ethernet cable. The changes cannot be made using the wifi.

Use the web interface to go to the Network section and the Interfaces subsection and click on the Edit button for the Lan interface. Since, by default, all ROOters have the 192.168.1.1 IP Address we must change the Client Router's IP Address to something different.

In this case it has been changed to 192.168.1.20 but you can change it to any unused IP Address.

Then we must turn off the DHCP server for this router. This is done because the Master Router is configured by default to be a DHCP server and only one of these is needed in a network. Scroll down the page to do this.

If the Master Router is supplying Internet to the network we must change the IPv4 Gateway to point to that router and to set up Custom DNS Servers. If the Client router is supplying Internet you can skip this part and just click on Save & Apply.

We must also specify a DNS Server in the Use Custom DNS Servers box. Shown is the IP Address of Google but you can substitute any DNS Server here.

Click on Save & Apply. The Loading screen will appear but you will not get back to the web interface because we changed the IP Address of the Client Router. We must change the IP Address in the web browser so we can access the web interface again. For this example use 192.168.1.20.

With the changes to the LAN complete we can start doing the Wifi linking.

Go to the Network menu and the Wifi submenu and click on the Scan button for the radio you are using as the link.

This will bring up a list of wifi access points in the area. Here the Master Router is named OpenWrt.

Click on the Join Network button for the Master Router.

If the Master Router's wifi is password protected, fill in the correct password in the WPA passphrase box. Make sure the LAN is selected in the Firewall Zone. Click on the Submit button in the lower right corner. This will return you to the Wifi Interface page.

Change the Mode to Client (WDS) and make sure the Lan is selected as the Network. Click on Save & Apply.

And lastly, we must disable the Firewall on the Client Router. Use the web interface to go to the Network menu and the Interfaces submenu and click on the Edit button for the Lan interface. Select the Firewall Settings tab.

Click on Save & Apply.

The Client Router must now be rebooted in order for the changes to be applied. After rebooting the Client Router will automatically connect to the Master Router and join the two networks using a WDS wifi link.

After doing this the Client Router no longer has a Wifi Access Point on it as that interface is used for the WDS link. The last thing that needs doing is to add a Wifi AP to the router.

Go to the Network menu and the Wifi submenu and click on the Add button for the radio you used for the WDS link.

This will create another wifi interface for the Client Router.

Make sure the ESSID is the same as the ESSID of the Master Router, set the Mode to Access Point (WDS) and the Network to Lan. Click on Save & Apply.

The Client Router now has a wifi access point with the same name as the Master Router.

When a device attempts to connect to the wifi of the newly created network it will connect to the router that has the strongest signal. If the device moves away from that signal source and closer to the wifi of the other router it will be seamlessly switched to the stronger signal when the current signal level drops below a certain point.

This allows a device to roam over the area covered by both router's wifi and never lose the connection.