Intermec MobileLAN 21 Series, System Manual, Page: 96 / 275

MobileLAN access 21XX System Manual
4-8
By default, wireless traffic is not bridged to a remote IP subnet. Any access point on a
remote subnet that can receive IP hello messages can establish an IP tunnel; therefore,
multiple IP tunnels can exist between the root access point and a single remote IP
subnet.
If bridging is disabled, all traffic for end devices is forwarded between access points
using data link encapsulation, which means that the MAC source/destination addresses
correspond to the access points originating/receiving the traffic for the end devices. By
using data link encapsulation, you prevent network monitoring tools and other network
components from detecting end device MAC/IP addresses that belong to the remote
subnet. Intermec strongly recommends using the default setting 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. There is no additional forwarding overhead for disabling bridging in this
situation.
If you enable bridging on a remote subnet, a single access point functions as the
designated bridge for the secondary LAN. In this case, only the designated bridge can
establish an IP tunnel. Any other access point on the remote subnet must attach to the
network through the designated bridge. End device MAC/IP addresses are fully visible
on the remote subnet. If you are using IP tunnels to provide mobility for IP and other
non-routable protocols, you can enable bridging on remote IP subnets, because IP has
built-in safeguards and filters for protecting the operation of IP routers and other
network components.
Also, you should enable bridging if the root access point and the Intermec gateway that
supports the Intermec NNL devices are on different IP subnets. You may also need to
enable bridging if your wireless end devices use terminal emulation running the NNL
protocol or if you use wireless end devices that are running both IP and NNL.
About Secondary LANs and Designated Bridges
There are two types of secondary LANs: one type is connected to the primary LAN via
an IP tunnel the other type is connected wirelessly to the primary LAN. For help
configuring IP tunnels, see “Configuring IP Tunnels” later in this chapter. For help
configuring a wireless secondary LAN, see “Configuring WAPs” in Chapter 5.
The access point that is responsible for bridging data between the secondary LAN and
the primary LAN is called the designated bridge. In both types of secondary LANs, the
designated bridge acts the same. The designated bridge must be an access point that has
at least one radio set to Station mode or is the endpoint of an IP tunnel. If more than one
access point meets at least one of these requirements, the access point with the highest
secondary LAN bridge priority is the designated bridge.