Wireless Residential Gateways

A wireless residential gateway is a device designed to connect a small number of wireless nodes to a single device for Layer 2 (wired and wireless) and Layer 3 connectivity to the Internet or to another network. Manufacturers have begun combining the roles of access points and gateways into a single device. Wireless residential gateways usually include a built-in hub or switch as well as a fully configurable, Wi-Fi compliant access point. The WAN port on a wireless residential gateway is the Internet-facing Ethernet port that may be connected to the Internet through one of the following:

Cable modem
xDSL modem
Analog modem
Satellite modem


Common Options
Because wireless residential gateways are becoming increasingly popular in homes of
telecommuters and in small businesses, manufacturers have begun adding more features
to these devices to aid in productivity and security. Common options that most wireless
residential gateways include are:

Point-to-Point Protocol over Ethernet (PPPoE)
Network Address Translation (NAT)
Port Address Translation (PAT)
Ethernet switching
Virtual Servers
Print Serving
Fail-over routing
Virtual Private Networks (VPNs)
Dynamic Host Configuration Protocol (DHCP) Server and Client
Configurable Firewall

This diverse array of functionality allows home and small office users to afford an all-inone single device solution that is easily configurable and meets most business needs. Residential gateways have been around for quite some time, but recently, with the extreme popularity of 802.11b compliant wireless devices, wireless was added as a feature. Wireless residential gateways have all of the expected SOHO-class access point configuration selections such as WEP, MAC filters, channel selection, and SSID.


Configuration and Management
Configuring and installing wireless residential gateways generally consists of browsing to the built-in HTTP server via one of the built-in Ethernet ports and changing the userconfigurable settings to meet your particular needs. This configuration may include changing ISP, LAN, or VPN settings. Configuration and monitoring are done in similar fashion through the browser interface. Some wireless residential gateways units support console, telnet, and USB connectivity for management and configuration. The text-based menus typically provided by the console port and telnet sessions are less user-friendly than the browser interface, but adequate for configuration. Statistics that can be monitored may include items such as up-time, dynamic IP addresses, VPN connectivity, and associated clients. These settings are usually well marked or explained for the nontechnical home or home office user.

When you choose to install a wireless residential gateway at your home or business, be
aware that your ISP will not provide technical support for getting your unit connected to the Internet unless they specifically state that they will. ISPs will usually only support the hardware that you have purchased from them or that they have installed. This lack of service can be especially frustrating to the non-technical user who must configure the correct IP addresses and settings in the gateway unit to get Internet access. Your best source of support for installing these devices is the manual provided with the device or someone who has already successfully installed similar units and can provide free guidance. Wireless residential gateways are so common now that many individuals that consider themselves non-technical have gained significant experience installing and configuring them.

Wireless LAN Client Devices

The term “client devices” will, for purposes of this discussion, cover several wireless LAN devices that an access point recognizes as a client on a network. These devices include:

PCMCIA & Compact Flash Cards
Ethernet & Serial Converters
USB Adapters
PCI & ISA Adapters

Wireless LAN clients are end-user nodes such as desktop, laptop, or PDA computers that need wireless connectivity into the wireless network infrastructure. The wireless LAN client devices listed above provide connectivity for wireless LAN clients. It is important to understand that manufacturers only make radio cards in two physical formats, and those are PCMCIA and Compact Flash (CF). All radio cards are built (by the manufacturers) into these card formats and then connected to adapters such as PCI, ISA, USB, etc.

PCMCIA & Compact Flash Cards
The most common component on any wireless network is the PCMCIA card. More commonly known as “PC cards”, these devices are used in notebook (laptop) computers and PDAs. The PC card is the component that provides the connection between a client device and the network. The PC card serves as a modular radio in access points, bridges, workgroup bridges, USB adapters, PCI & ISA adapters, and even print servers. The following figure shows an example of a PCMCIA card.
Antennas on PC cards vary with each manufacturer. You might notice that several
manufacturers use the same antenna while others use radically different models. Some
are small and flat such as the one shown in the above figure, while others are detachable and connected to the PC card via a short cable. Some PC cards are shipped with multiple antennas and even accessories for mounting detachable antennas to the laptop or desktop case with Velcro.

Wireless Ethernet & Serial Converters
Ethernet and serial converters are used with any device having Ethernet or legacy 9-pin
serial ports for the purpose of converting those network connections into wireless LAN
connections. When you use a wireless Ethernet converter, you are externally connecting
a wireless LAN radio to that device with a category 5 (Cat5) cable. A common use of
wireless Ethernet converters is connection of an Ethernet-based print server to a wireless network.

Serial devices are considered legacy devices and are rarely used with personal computers. Serial converters are typically used on old equipment that uses legacy serial for network connectivity such as terminals, telemetry equipment, and serial printers. Many times manufacturers will sell a client device that includes both a serial and Ethernet converter in the same enclosure.

These Ethernet and serial converter devices do not normally include the PC card radio.
Instead, the PC card must be purchased separately and installed in the PCMCIA slot in
the converter enclosure. Ethernet converters in particular allow administrators to convert a large number of wired nodes to wireless in a short period of time.

Configuration of Ethernet and serial converters varies. In most cases, console access is provided via a 9-pin legacy serial port. The above figure shows an example of an Ethernet and serial converter.


USB Adapters
USB clients are becoming very popular due to their simple connectivity. USB client
devices support plug–n-play, and require no additional power other than what is delivered through the USB port on the computer. Some USB clients utilize modular, easily removable radio cards and others have a fixed internal card that cannot be removed without opening the case. When purchasing a USB client device, be sure you understand whether or not the USB adapter includes the PC card radio. In cases of a USB adapter that requires a PC card, it is recommended, although not always required, that you use the same vendor’s equipment for both the adapter and the PC card. Figure 4.14 shows an example of a USB client.


PCI & ISA Adapters

Wireless PCI and ISA are installed inside a desktop or server computer. Wireless PCI
devices are plug–n–play compatible, but may also only come as an “empty” PCI card and
require a PC card to be inserted into the PCMCIA slot once the PCI card is installed into the computer. Wireless ISA cards will likely not be plug-n-play compatible and will require manual configuration both via a software utility and in the operating system. Since the operating system cannot configure ISA devices that aren’t plug-n-play compatible, the administrator must make sure the adapter’s setting and those of the operating system match. Manufacturers typically have separate drivers for the PCI or ISA adapters and the PC card that will be inserted into each. As with USB adapters, it is recommended that you use the same vendor’s equipment for the PCI/ISA adapters and the PC card. The above figure shows an example of a PCI adapter with a PC card inserted.

Wireless Workgroup Bridges

Similar to and often confused with wireless bridges are wireless workgroup bridges (WGB). The biggest difference between a bridge and a workgroup bridge is that the workgroup bridge is a client device. A wireless workgroup bridge is capable of aggregating multiple wired LAN client devices into one collective wireless LAN client.

In the association table on an access point, a workgroup bridge will appear in the table as a single client device. The MAC addresses of devices behind the workgroup bridge will not be seen on the access point. Workgroup bridges are especially useful in environments with mobile classrooms, mobile offices, or even remote campus buildings where a small group of users need access into the main network. Bridges can be used for this type of functionality, but if an access point rather than a bridge is in place at the central site, then using a workgroup bridge prevents the administrator from having to buy an additional bridge for the central site.


In an indoor environment in which a group of users is physically separated from the main body of network users, a workgroup bridge can be ideal for connecting the entire group back into the main network wirelessly. Additionally, workgroup bridges may have protocol filtering capabilities allowing the administrator to control traffic across the wireless link.

Common Options
Because the wireless workgroup bridge is a type of bridge, many of the options that you will find in a bridge – MAC and protocol filtering, fixed or detachable antennas, variable power output, and varied types of wired connectivity – are also found in a workgroup bridge. There is a limit to the number of stations that may use the workgroup bridge from the wired segment. This number ranges between 8 and 128 depending on the manufacturer. Use of more than about 30 clients over the wireless segment is likely to cause throughput to drop to a point at which users might feel that the wireless link is simply too slow to adequately perform their job tasks.

Configuration and Management
The methods used to access, configure, and manage a wireless workgroup bridge are similar to those of a wireless bridge: console, telnet, HTTP, SNMP support, or custom configuration and management software. Workgroup bridges are configured for a default IP address from the manufacturer, but can be changed either by accessing the unit via console port, web browser, telnet, or custom software application. The administrator can reset the device to factory defaults by using the hardware reset button on the device.