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Therefore, the RM-240 client must act as a proxy for devices lying on its wired Ethernet
port, and use its own MAC address on their behalf. To do this, it analyzes the IP addresses
within the Ethernet frame body and builds a lookup table so that when radio traffic is
received it can lookup the device MAC address based on its IP address. This functionality
is referred to as
Layer 3 Bridge
. Note that because the layer 3 bridge relies on IP, it is only
suitable for bridging Ethernet frames from devices that communicate using IP. For this
reason the bridge Spanning Tree Protocol
can not
be used with 3-address mode. When a
RM-240 client/station uses 3-address mode any Access Point that it is to communicate
with may be configured for either 3 or 4 address mode (i.e. Access Point mode does not
matter).
4-address mode allows a RM-240 client/station to bridge traffic from devices connected
to its wired Ethernet port without acting as a proxy for their MAC address. This means
that a RM-240 client/station in 4-address mode can bridge
any
Ethernet traffic – not just
IP based traffic as with 3-address mode. 4-address mode should also be used if the bridge
Spanning Tree Protocol is required. When a RM-240 client/station uses 4-address mode
any Access Point that it is to communicate with must also be configured for 4-address
mode.
Router Operation
A router joins separate Ethernet networks together. The router has different IP addresses
on its wired and wireless ports, reflecting the different IP addresses of the separate
Ethernet networks. All the devices in the separate networks identify the router by IP
address as their gateway to the other network. When devices on one network wish to
communicate with devices on the other network, they direct their packets at the router
for forwarding.
As the router has an IP address on each of the networks it joins, it inherently knows the
packet identity. If the traffic directed at the router can not be identified for any of the
networks to which it is connected, the router must consult its routing rules as to where
to direct the traffic to. For details on configuring routing rules see section “3.11 Routing
Rules”.