Intermec WA21 System Manual page 118

Chapter 5 — Configuring the Spanning Tree
104
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 switch–the port that is connected to the root access point or
designated bridge.
• 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.
3 On all other access points on the primary LAN, clear the Enable
Ethernet Bridging check box.
4 Make sure that the Root Priority parameter for all other access points is
less than the root access point.
To enable data link tunneling on the secondary LAN
1 Make sure that all access points have the same LAN ID as the ones on
the primary LAN.
2 On the designated bridge, on the Spanning Tree Settings screen verify
that the Enable Ethernet Bridging check box is checked.
3 On all other access points on the secondary LAN, clear the Enable
Ethernet Bridging check box.
4 Make sure that the Secondary LAN Bridge Priority parameter for all
other access points is less than the designated bridge.
If you use data link tunneling on the secondary LAN and end devices have
IP addresses on the secondary LAN, network monitoring tools and other
network components cannot detect their MAC/IP addresses. For more
information, see "About IP Tunnels" on page 108.
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