802.11 roaming

Roaming in a wireless LAN ----
Configuration and application of wireless roaming
At present, wireless networks have quietly become the new favorite of modern office work, but the coverage of a single AP is limited. Therefore, some companies with large coverage often place two or more aps, wireless networks can be used within the company, but this is a problem. When mobile users switch between different APs, they need to find the wireless network each time, it is very troublesome to reconnect. Is there a good way? The wireless roaming solution can easily solve this problem.
What is roaming )?
When deploying a wireless LAN in a large enterprise with a large network span, some employees may need full mobile communication capabilities, which requires a wireless roaming connection solution. Due to the constant attenuation of radio waves during the re-propagation process, the communication range of Wireless AP is limited to a certain distance. When multiple APS exist in the network environment, their signal coverage will overlap. Then, they will be connected by a network cable, wireless Client users can move in any region covered by different aps to maintain network connections. This is wireless roaming. When used, the wireless network adapter can automatically discover the AP with the highest signal strength nearby, and send and receive data through this AP to maintain uninterrupted network connections. I believe everyone has used mobile phones. When mobile phones are moved from the coverage of one base station to the coverage of another base station, they can provide uninterrupted and seamless calls. This is the use of the wireless roaming function.
In fact, the roaming function of a wireless LAN is exactly the same as that of a mobile phone.
How to configure wireless roaming:
1. Wireless AP Configuration:
Because wireless roaming must be composed of multiple APs, each AP must be allocated in advance.
And ensure that the ap ip address is in the same CIDR block. The same Essid must be set! To ensure the security of the wireless network, we can perform WEP encryption on the AP, but the encryption method and the encryption secret must be the same! Disable the Broadcast SSID. If necessary, you can also set the MAC address filter to prevent illegal clients from intruding into your LAN through wireless networks.
In order to achieve roaming, We must overlap the signal coverage of multiple APs. If there is a channel with overlapping signals, they interfere with each other during signal transmission, reducing network performance and efficiency. Therefore, the channels occupied by AP coverage areas must follow certain standards. aps in overlapping 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. Using these three channels for cellular coverage is the most suitable.

Instance:

At the beginning of this article, pay special attention to two issues:

1. Prerequisite for WLAN Roaming: The SSID must be consistent during the roaming process and the same security settings must be used.

2. In roaming, select the AP to connect to. The time and speed of switching are determined by the chip or settings of the wireless client, therefore, the number of packet loss on each client may vary during the roaming switching process. But under normal circumstances, the switch should be successful.

I. Deficiencies in traditional 802.11 Wireless mobility

L there is no standard protocol for switching between APS

L no standard protocol for client-AP Switching

L The wireless client is associated with an AP and will be associated with the AP as much as possible

L only when the error rate reaches a certain level will the wireless client disconnect the original association and turn to the new AP

L in traditional fat AP networks, wireless clients need to re-Authenticate and obtain new IP Addresses During roaming, and all data transmission will be interrupted. (Some manufacturers have improved this, but specialized software/client support is required .)

Ii. Features of wfs709tp Wireless Mobile

L because wfs709tp provides centralized management for wireless transmission, wireless roaming is seamless.

L when a client roaming from one AP to another, it only needs to change the wireless channel. The wireless controller maintains the authentication and encryption status of the client.

3. Independent controller roaming (only one wfs709tp in the environment)

1. l2 (Layer 2) Roaming

Note: AP1 (1.1.1) and AP2 (1.1.2) are on the same wfs709tp, And the broadcasted SSID is the same and on the same VLAN. When the client is roaming from 1.1.1 to 1.1.2, the IP address and encryption of the client are maintained in wfs709tp. During the roaming process, no IP address changes or re-Authentication occurs. Only wireless channels have changed.

2. l3 roaming

Note: AP1 (1.1.1) and AP2 (1.1.2) are on the same wfs709tp. The SSID for broadcasting is the same but different VLANs. When the client is roaming from 1.1.1 to 1.1.2, the Controller regards the client as connected from the original VLAN, allowing the client to maintain its original IP address and support established IP communication.

In the above example, when a user roaming from the SSID (Netgear) under the original VLAN 100 to the same SSID (Netgear) under VLAN 200 ), the client's IP address does not change because of VLAN changes. Instead, it uses the IP address originally in VLAN 100 for communication.

4. Cross-controller roaming (roaming between multiple wfs709tp instances in master-Local Mode)

1. l2 (Layer 2) Roaming

NOTE: If two or more controllers are layer-2 connections, use trunk to connect all user VLANs on all controllers. When a user is roaming to an AP under another controller, the new controller processes user traffic in the original VLAN.

In the preceding example, the user first browsed the SSID (Netgear) under VLAN 100 of controller 1 to the same SSID (Netgear) under VLAN 200 of controller 2 ), the client's IP address does not change because of VLAN changes. Instead, it uses the IP address originally in VLAN 100 for communication.

2. l3 roaming

Note: L3 roaming is used when controllers are divided into different subnets. The Controller establishes a mobile-IP tunnel to transmit client traffic to the original controller (home agent ). When a client is roaming from an AP controller to another controller, the new controller (foreign agent) identifies the client and transmits traffic to the original controller (home agent) through a tunnel ).

In the preceding example, the user first browsed the SSID (Netgear) under VLAN 100 of controller 1 to the same SSID (Netgear) under VLAN 200 of controller 2 ), the client's IP address does not change because of VLAN changes. Instead, it uses the IP address originally in VLAN 100 for communication.

5. wfs709tp roaming settings

Enabling the wfs709tp roaming function is very simple. You only need to go to the configuration> advanced> controller> General of the master, and check the enable mobility under the mobility configuration, click Apply, wireless roaming is enabled.

6. Client Status display

In monitoring> controller> clients, you can see the status of the client, such:

There are three statuses in total:

1) associated: indicates that the client is normally connected to the AP on the local controller, and no cross-VLAN roaming occurs.

2) Visitor: the client is connected to the AP of another controller, or another AP on the local controller. After three layers of roaming, the client reaches the AP on the local controller. This is the Client IP address or the IP address of the original VLAN.

3) away: the client is originally connected to the local controller, and then roaming to another AP or another controller through three layers. In this case, the Client IP address is still the IP address of the original VLAN.