Wireless Interconnection of ROOters

You can link several ROOters together using the wifi on the router to supply Internet to another network or join two networks together into one. There are several different methods of doing this, depending on what you are looking to achieve.

    Description
   
Introduction Introduction to wifi linking
Link Speed Speed of the wifi link
Routed Client Mode Internet Only mode of linking
Wifi for Client Wifi access point for the Client router
Wireless Distribution System WDS mode of linking
Wifi for Client Wifi access point for the WDS Client router

 

Introduction

In this tutorial, we will look at two different methods of connecting routers and their networks together using wifi. These methods can either supply internet from one network to another or can join two networks into one large one, complete with wifi roaming.

Internet Only

If you want to supply one network with internet from another you would use the Routed Client method, also known as the Internet Only method. The devices on one network can not access the devices on the other network using this method. Only internet is shared between the netwoks.

One example of this would be supplying Internet from one house to another, where you don't want the people from one house accessing the other house's network.

An advantage to this method is the router supplying the internet for both networks does not have to be a ROOter and can be factory stock, as no modifications need to be done to it.

Wireless Distribution System

This method, also known as WDS, is much more powerful than the Routed Client method and is used when you wish to join two netwoks together into one large network without needing an Ethernet connection between them. The devices on one network can access devices on the other network using this method.

Wifi roaming is also supported by WDS so your wireless devices will connect to the strongest wifi signal and be handed off to the other wifi signal when the first one becomes too weak.

The disadvantage to this method is that both routers must be a ROOter, since modifications must be made to both routers. Also, both routers must use the same Atheros wifi chipset. Of the supported ROOters only the Netgear WNR3500L doesn't use this 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. This is set in the Advanced Setting of the Wifi Interface. WiFi has a system spectral efficiency of 2.44 bits/Hz, so 20MHz gives (at most) 48.8Mbps while 40MHz gives at most 97.6Mbps.

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 setting both Master and Client Router to 40Mhz wifi width. This should be done to maximize the speed of the wifi link, regardless of the mode used.

Routed Client or Internet Only Mode

 

The two routers can have the same IP Address, as shown above, since the networks are totally separate except for the Internet access.

To create a wifi link between the Master and the Client Routers we must change certain things on the Client Router using the web interface.

Connect the Client Router to your computer using an Ethernet cable. This procedure can not be done using the wifi.

If you have been making changes to the Client Router it is best to set it back to an 'as flashed' state by holding in the reset button for more than 17 seconds and less than 60 seconds. The router will reboot after this and will appear in the same configuration as it was when you flashed it. This will remove any changes made to the router previously.

To set up the Client Router, go to the Network section and the Wifi subsection and click on the Scan button.

This will bring up a list of wifi access points in the area. For this tutorial the Master Router is named dd-wrt.

Click on the Join Network button of 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.

Click on Save & Apply in the lower right corner.

Next, go to Network->Interfaces and Edit the WWAN entry. Click on the Firewall Settings tab and make sure it looks like this :

If it isn't, change it and click on Save & Apply in the lower right corner.

The Client Router is now linked by wifi to the Master Router and is supplying Internet to any devices connected to it's LAN.

Adding A Wifi Access Point

If you wish to use the wifi on the Client Router as an access point, so devices can access the Client network wirelessly, it is possible to do so at the expense of halving the speed of the wifi link. This means the wifi link will have a maximum speed of 44Mbs. Unless you have very fast Internet this will not normally be a problem.

Once again, we must modify the Client Router by using the web interface. Go to the Network section and the Wifi subsection and click on the Add button.

This will create another wifi interface for the Client Router.

Fill in the ESSID with the name you wish to give this access point, set the Mode to Access Point and make sure the Network is set to the LAN. Click on Save & Apply in the lower right corner.

Next, go to Network->Interfaces and Edit the LAN entry. Click on the Physical Settings tab and make sure it looks like this

If it isn't, change it and click on Save & Apply in the lower right corner.

The Client Router now has a wifi access point attached to it that can access the Client's network.

If you wish to make this wifi access point secure click on the Wireless Security tab and set up a password and encryption method for it.

Fill in the necessary data and click on Save & Apply in the lower right corner. Wait until the changes are applied.

Wireless Distribution System (WDS)

 

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.

Both the Master and Client Routers need to have some changes made to them in order to set up the WDS wifi link. We will look at these individually.

Master Router Changes

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 section and the Wifi subsection and click on the Edit button for the wifi interface.

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 with it. 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 section and the Interfaces subsection 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.

The changes to the Master Router are now complete.

Client Router Changes

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

Because there is a chance that your computer will not be assigned an IP Address during these changes, it is best if you set your computer to use a static IP Address while making the changes and then set it back to Automatic when the changes are finished. See Setting a Static IP on your Computer for details.

If you have been making changes to the Client Router it is best to set it back to an 'as flashed' state by holding in the reset button for more than 17 seconds and less than 60 seconds. The router will reboot after this and will appear in the same configuration as it was when you flashed it. This will remove any changes made to the router previously.

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. Click on Save & Apply.

Because we changed the IP Address of the Client Router we must also change the IP Address in the web browser so we can access the web interface again.

Once again, use the web interface to go to the Network section and the Interfaces subsection and click on the Edit button for the Lan interface. If the Master Router is supplying Internet to the network we must change the IPv4 Gateway to point to that router.

If the Client Router is supplying Internet to the network then you do not need to set the IPv4 Gateway or the Custom DNS Servers.

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.

And lastly, 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.

Now click on Save & Apply and wait for the changes to take place.

Next, go to the Network section and the Wifi subsection and click on the Scan button.

This will bring up a list of wifi access points in the area. For this tutorial 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.

Make sure that the Lan is still selected as the Network, as this has a habit of changing when altering other sections.

And lastly, we must disable the Firewall on the Client Router. Use the web interface to go to the Network section and the Interfaces subsection 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 jion the two networks using a WDS wifi link.

If you set your computer to use a static IP Address go back and set it to Automatic again.

Adding a Wifi Access Point

One of the features of the WDS wifi link is, if you have a wifi access point on the Client Router, any device connecting to the wifi can roam around the area covered by both router's wifi and be seamlessly switched between the router's wifi to maintain a strong signal.

The disadvantage to this is the WDS wifi link's speed will be halved to a maximum of 44Mbs.

We must modify the Client Router by using the web interface. Go to the Network section and the Wifi subsection and click on the Add button.

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 devices 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.