Proving the Universal Repeater mode of TP-Link Wireless Access Points

It is sometimes necessary to work with wireless networks as part of a client's larger project. I have become something of a specialist in wireless network configuration, including the standard combined ADSL modem/router/access point/switch/firewall devices used domestically and in small offices, as well as corporate Wireless Access Point (AP) configuration. These devices were formerly very expensive considering that the AP component of a home router does broadly the same job, but the extra cost could be attributed to higher quality components, often Power over Ethernet support (PoE), more reliable firmware and the remote management featureset allowing a network admin to query the device and change settings. Prices of over £100 could be expected.

TP-Link seems to be a relative newcomer to the Wireless Access Point scene. They have produced a wide range of innovative devices so far. An example would be the TL-WA701D 150Mbps Wireless N Access Point, which retail at a very acceptable £25. They support PoE and a variety of other features but what makes them interesting to me is the various ways they can be configured. From the firmware's own help guide (grammar errors their own):

Access Point - This operation mode allows wireless stations to access.

Multi-SSID - AP can support up to 4 SSID.

Client - This device will act as a wireless station to enable wired host(s) to access AP.

Repeater - In Repeater mode, the AP with WDS enabled will relays data to an associated root AP. AP function is enabled meanwhile. The wireless repeater relays signal between its stations and the root AP for greater wireless range. Please input the MAC address of root AP in the field "MAC of AP".

Universal Repeater - In Universal Repeater mode, the AP with WDS disabled will relays data to an associated root AP. AP function is enabled meanwhile. The wireless repeater relays signal between its stations and the root AP for greater wireless range. Please input the MAC address of root AP in the field "MAC of AP".

Bridge with AP - This operation mode bridges the AP and up to 4 APs also in bridge mode to connect two or more wired LANs. Please input the MAC address of other APs in the field "MAC of AP1" to "MAC of AP4". AP function will also startup.

So in a very reasonably priced device you have a wireless network bridge for one purpose, and a quick switch over to being an Ethernet connected client which is far more stable than a USB wireless dongle.

There is one big disappointment, though. The configuration, although seemingly straightforward is not easy for each mode and requires a lot of trial and error. Let's look at the Universal Repeater mode, which is an excellent feature but a good example of configuration gone mad.

The Universal Repeater mode provides a way to extend a wireless network which either does not support WDS (the recognised protocol for achieving the same) or supports WDS poorly. The idea is simply that the AP acts as both a client on the host network, whilst simultaneously bridging for any of its own clients. The cost? A halfing of throughput. In practical terms this is not much of a limitation where users are mainly concerned with getting online. Naturally if file sharing within the property must be done at high speed, an alternative (probably cabled or making use of Homeplug powerline technologies) might be more suitable. As domestic broadband is rarely more than 20Mbps, a halving of 150Mbs on an N-class wireless network leaves loads of headroom and no internet slowdown will be noticable. A greater issue occurs when the domestic network is running at 802.11g speeds or slower, but even with a VDSL connection to BT's new 21st Century feature: Fibre to the Cabinet (FTTC) or "Infinity" as it is branded, only users on the 100Mbps service should feel any slowdown at all, and that is if the websites and file sharing they're using is also connected that fast.

So, on to the configuration. It is best to approach it in this order, so as to minimise the number of device reboots and network configuration changes on the computer used to set things up.

Fire up the TP-Link box and connect to it with Ethernet. No DHCP server will be running on the device for starters, so configure the setup computer with these static TCP/IPv4 settings:

IP address: 192.168.1.10 (or something in that subnet)

Subnet mask: /24 or 255.255.255.0

Gateway: 192.168.1.254

Next, log into the TP-Link web interface. You should find it at http://192.168.1.254

Wireless Security settings should be set to those of your host router/Access Point - the one you want to extend

Wireless Settings should be switched to Universal Repeater and your host AP should be scanned for and selected for connection.

Finally, the Network settings must be changed. I have had most success by picking a new IP for the TP-Link in the same subnet as the host network. The gateway should be the same as the IP of the host network router. A reboot of the router is necessary after this step.

For best results, disable the built-in DHCP server.

Optionally, enable the Ping Watchdog in the System Tools. You can give it the IP of the host router. If it goes down for a predefined time, the AP will assume that there is a fault and will reboot itself.

Testing the connection is as easy as disconnecting the Ethernet cable and connecting via wireless. Ideally, you should do so from an endpoint which can reveal the BSSID of the AP you're accessing. In Linux, iwconfig can tell you that. With Android, WiFi Manager is the app to use: just click the network to see its physical ID.

Of course, if all has gone well, it should be clear from the better connection strength that you're online via the repeater.