Networking of Wireless AP

WLAN (Wireless Local Area Network) is a combination of computer networks and wireless communication technologies. Specifically, traditional cables are no longer used to establish a LAN, and infrared and radio waves are used as transmission media to connect to the LAN in a wireless manner, providing all functions of the LAN. The basis of the wireless LAN is the traditional wired LAN, which is the extension and replacement of the wired LAN, on the basis of a wired LAN, it implements wireless communication through wireless hubs, wireless access nodes, wireless bridges, wireless NICs, and other devices. At present, wireless LAN is mainly used in the S band (GHz ~ 2.4835 GHz ).

Generally, the networking mode of a wireless LAN can be divided into two types: Ad-Hoc Mode (point-to-point wireless network) and Infrastructure mode (Centralized Control Network.

1. Ad-Hoc Mode

An ad-hoc network is a point-to-point peer-to-peer mobile network without the support of wired infrastructure. nodes in the network are composed of mobile hosts. Wireless AP does not exist in the network. Multiple wireless network adapters can be used for communication. Shows the basic structure:

 

To create a peering network, follow these steps:

1) First, install a wireless network card for your computer, and configure network parameters such as IP addresses for your wireless network card. Note: the IP address of the host to be connected must be in the same CIDR block. Because the peer network does not have a gateway, you do not need to enter the gateway.

2) set the working mode of the wireless network card to ad-hoc, and configure the same SSID, frequency band, encryption mode, key and connection rate for the network card to be connected.

Note: TP-LINK full range of wireless network card products support this application mode.

2. Infrastructure mode

Centralized Control Network is an application mode that integrates wired and wireless LAN architectures. In this mode, the wireless network adapter and the Wireless AP are connected wirelessly, and then the Wireless AP is connected to the wired network. In fact, the infrastructure network can be divided into two modes: one is the connection mode between a wireless router and a wireless network card, and the other is the connection mode between a Wireless AP and a wireless network card.

The "wireless router + wireless nic" mode is currently used by many families. In this mode, a wireless router is equivalent to a Wireless AP that integrates the routing function to connect a wired network to a wireless network. For example, our wireless router series not only integrates Wireless AP and routing functions, but also integrates a wired four-port switch to achieve hybrid connection between a wired network and a wireless network, as shown in:

 

 

The other is the "Wireless AP and wireless network card" mode. In this mode, how to set up a Wireless AP and establish a connection with a wireless or wired Nic depends on the specific functions you want to implement and the devices you want to use. Because Wireless AP has multiple working modes, different working modes may connect to different devices, and the connection methods may not be the same. The following is our Wireless AP TL-WA501G (hereinafter referred to as 501g) Working Mode and Its settings. Our 501g supports five basic working modes: AP mode, AP client mode, repeater mode, bridge (Point to Point) mode, and bridge (point to multi-point) mode.

1) AP Mode

AP (Access Point mode), which is the basic working mode of Wireless AP. It is used to build a centralized control network centered on Wireless AP. All communications are forwarded through AP, similar to the function of a vswitch in a wired network. In this mode, the connection mode is roughly shown in:

 

 

In this mode, the Wireless AP can establish a wireless connection with the wireless network card, or establish a wired connection with the wired network card through the network cable. Our 501g has only one LAN port. Generally, it is not used to connect directly to the computer. Instead, it is used to establish a connection with the wired network and directly connect to the front-end router or switch. In this mode, the specific settings for our 501g are shown in:

 

 

The first step is to set the frequency band for the Network to work. The range is from 1 to 13. Note that if there are other wireless networks in the surrounding environment, try not to use the same frequency segment as it. Then select the 501g mode. Our 501g mode supports 11 mbps bandwidth of 802.11b and 54mbps of 802.11g mode (compatible with 802.11b mode ). When enabling the wireless function, do not select the 'Disable wireless function' option. Select the 'Access point' option and set the SSID number. Note: The SSID number set on the wireless card that establishes a connection with our Wireless AP must be the same as that set on the Wireless AP. Otherwise, the network cannot be connected.

2) AP client Mode

In AP client mode, a computer connected to a Wireless AP can only connect to the AP in wired mode, but cannot connect to the AP in wireless mode. The connection method for a Wireless AP working in AP client mode is roughly shown in:

 

 

The wireless device A in the figure can be a wireless router or a Wireless AP. When we need to use our GB wireless connection to establish a wireless connection with our wireless router, the settings on the Wireless AP are shown in:

 

 

In client mode, a Wireless AP can be connected to a front-end wireless router in two ways. One is to connect a wireless router by setting the same SSID number as the wireless router; another method is to establish a connection by entering the MAC address of the LAN port of the wireless router in 'ap Mac address.

● Enable WDS-If WDS is enabled, the 4-address package format will be used to communicate with the AP; otherwise, the 3-address package format will be used. (Compatibility with front-end wireless routers)
● SSID-specify the SSID to select an AP.
● MAC address of the AP-specify the MAC address to access the AP.

Note: currently, all wireless routers in our company support WDS. Therefore, whether to disable WDS on wa501g can be connected.
When a Wireless AP working in AP client mode establishes a connection with another Wireless AP, the connected Wireless AP can be in AP mode or repeater mode that retransmits the front-end signal. When the current AP is set to repeater mode, it does not have an SSID number. Therefore, the Wireless AP set to AP client needs to establish a connection with it, you can only enter the MAC address of the front-end ap in the 'ap Mac address' column for connection.

3) Bridge (Point to Point) Mode

In the current wireless bridge mode, a Wireless AP can be connected to a wireless network card in wireless mode, and can also be connected to a computer using a wireless ap lan port. In this mode, the two APs are usually set to the Bridge Mode for connection, the effect is equivalent to a network cable to connect the two LAN ports. The specific connection is shown in:

 

 

A Wireless AP in bridging mode can enable its ap function to connect to a wireless workstation. You can also specify the MAC address of the AP to be connected for bridging. The interface is shown in:

 

In Bridge Mode, set the MAC address of the Peer AP to connect to the peer AP. Note that the two wireless APS must have the same operating frequency. Otherwise, the connection may fail. Of course, whether in the vro or wa501g + configuration, you need to consider the entire network gateway, DHCP server and other issues.

4) Bridge (point to multi-point) Mode

In the wireless multi-bridge mode, a Wireless AP can work with up to four aps in the bridge mode to build a point-to-point wireless network. The AP function can also be enabled. Shows the basic mode:

 

The figure shows three wireless APs, A, B, and C. Both A and C are set to the bridge mode, and the Wireless ap B is set to the Multi-Channel Bridge Mode. Both A and C are set to point to B, enter the MAC address of ap B. Add the MAC addresses of AP A and AP C to establish a connection. In a Wireless AP that is set to multi-bridge mode, you need to fill in multiple topics for entering the MAC address. If there are fewer than two entries, an error will be reported during saving. That is to say, when the Wireless AP is set to multi-bridge mode, it must be connected to at least two other wireless APs. In our 501g multi-bridge mode, we can connect to up to four wireless APs at the same time. If the AP function is enabled, B can connect to the wireless workstation. Shows the setting interface:

 

 

5) Repeater Mode

In wireless relay mode, a Wireless AP is used to zoom in and resend signals. Therefore, it can be connected to a Wireless AP set to AP mode and relay its signals. Wireless AP in repeater mode can also be connected to a Wireless AP in repeater mode. As shown in:

 

 

The repeater Wireless AP is mainly used to expand the coverage of wireless networks. Assume that the computers under B and D need to communicate with each other, but the signal of B cannot reach D. Therefore, we can add a Wireless AP in the middle to relay the signal of B, to realize the communication between B and D. We can set B to AP mode, C to relay B, and D to relay C so that B and D can communicate with each other. Set C as a relay for B. You only need to enter the MAC address of B in the 'ap MAC address 'column of C. As shown in:

 

 

● The Universal mode refers to the use of non-WDS mode to communicate with the AP, with more extensive compatibility.

At present, wireless networks have become a new favorite of modern and fashionable offices, but the coverage of a single AP is limited, therefore, companies with large coverage often place two or more wireless aps to expand the coverage of wireless networks. However, mobile users need to find the wireless network and reconnect to the Wireless AP each time when switching between different wireless APs, which is very troublesome. In this case, we have introduced a new concept of wireless roaming.

Wireless signals are constantly reduced during transmission, so that the AP communication range is limited to a certain range. This range is usually called micro-unit. When multiple wireless APS exist in the network environment and their micro-units have a fixed range for each other, wireless users can move within the entire range of wireless signal coverage. the wireless network adapter can automatically discover the Wireless AP with the highest signal strength nearby and send and receive data through this AP, keep uninterrupted network connections, which is called wireless roaming.

In practical applications, wireless networks sometimes have only one exit, so the following applications are used. Shows a Seamless Roaming network composed of four wireless APs. The four wireless APs are connected to the wired network through the network cable to form a wired network-based wireless network, all terminals connect to the network through the nearest Wireless AP to access the entire network resource. To achieve Seamless Roaming, we must first assign an IP address to each Wireless AP and ensure that the IP addresses of all wireless APs are in the same CIDR block. Each Wireless AP is set to AP mode, and the configured SSID must be the same. If you want to set encryption, the encryption method of the Wireless AP and the encryption key must be the same. In addition, it is best to retain the DHCP function in the upstream wireless router and disable the DHCP function of the Wireless AP. Otherwise, the IP address allocation will be chaotic.

 

 
 

As shown in the figure, to achieve roaming, some Wireless AP coverage overlaps with each other. If a channel with overlapping signals is used, then their signals will interfere with each other during transmission, thus reducing network performance and efficiency. Therefore, the channels occupied by the coverage areas of each AP must follow certain standards. APs with overlapping coverage areas cannot use the same channel. The 802.11b protocol works at 2.4000ghz ~ There are 11 overlapping channels in the 2.4835ghz channel. Only three of these 11 channels do not overlap, namely, Channels 1, 6, and 11, as shown in:

 

 

Therefore, it is most appropriate to use these three channels for Seamless Roaming. If you configure simple wireless roaming, you only need to set the roaming area to the overlapping area of each Wireless AP and the SSID number of each AP. The encryption method is the same.

This article from China protocol analysis network | www.cnpaf.net Original article links: http://www.cnpaf.net/Class/WLAN/200902/23332.html