Chapter 5: Configuring the Spanning Tree
About Ethernet
Bridging/Data
Link Tunneling
Ethernet bridging is simply forwarding a frame received on the radio port to the Ethernet port, and vice versa. Using this default mode, the access point acts as a bridge between the wireless and wired networks.
Note
Allied Telesyn recommends that you enable Ethernet bridging on all access points. However, if you meet the criteria listed later in this section, you can disable Ethernet bridging and use data link tunneling instead. Be aware that data link tunneling increases network traffic.
Turning off Ethernet bridging enables data link tunneling. The data link tunneling mode causes the child access point to encapsulate inbound wireless data into an 875C frame. This data frame is then forwarded via the Ethernet port to the next access point on the path, and so on, until the frame reaches the root access point or designated bridge. The root access point or designated bridge encapsulates the frame and forwards it to the host. When the root access point or designated bridge receives data on the Ethernet network for an end device, it reverses this process.
When should you use data link tunneling?
Use data link tunneling if you have Ethernet switches that do not support the IEEE 802.1d requirements for backward learning. Some proprietary VLAN switches and ATM LANE bridges do not support this standard.
If the access points are connected to different ports on an Ethernet switch, each time an end device roams to a new access point, it appears on a different port. Thus, frames sent to the end device from the host are sent to the wrong port. If the switch does not support 802.1d, it may become confused and communications with the end device are disrupted. Data link tunneling makes end device roaming transparent to the switch. All the information appears to originate from only one port on the
Use data link tunneling when you are using IP tunnels to provide mobility of other routable protocols, such as IPX. In some network installations, detecting these addresses may generate alarms or cause switches to behave erroneously. In this situation, using data link tunneling does not increase network traffic.
To enable data link tunneling on the primary LAN
1.Make sure that all access points have the same LAN ID.
2.On the root access point, on the Spanning Tree Settings screen verify that the Enable Ethernet Bridging check box is checked.
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