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Cooper Bussmann BU-245U-E Wireless Ethernet & Device Server User Manual
3.15 Routing Rules
When a BU-245U-E receives an IP frame that is destined for an IP address on a different network, it checks if the network address matches the
network address of one of its own interfaces (i.e., hard-wired Ethernet, or wireless Ethernet, or WDS) and forwards the frame appropriately.
However, if the IP network address does not match the network address of any of its interfaces, the BU-245U-E will forward the frame to its
default gateway. In this case it is assumed that the default gateway has a valid route to the destination.
In some cases, it is not practical to have just one default gateway (i.e., routed wireless networks with more than two BU-245U-E routers; and in
some cases when WDS router interfaces are used). If more than one “next-hop router” is required, the BU-245U-E allows for up to 30 routing
rules to be configured. A routing rule specifies a destination network (or host) IP address and the corresponding next-hop router that messages for
the specified destination will be forwarded to. It is assumed that the next-hop router (or gateway) will then deliver the data to the required
destination (or forward it on to another router that will).
The above network diagram illustrates a situation where routing rules may need to be configured. In this example, the BU-245U-E clients need
only specify the Access Point as their default gateway (i.e., they require no routing rules be configured). However, for the Access Point to be able
to deliver traffic to LAN B and LAN C it needs to have routing rules configured that specify the respective BU-245U-E client/routers as next-hop
routers (i.e., gateways) to networks B and C. Note that devices on LAN A should specify the BU-245U-E Access Point as their default gateway. An
alternative to adding routing rules to the BU-245U-E in this example would be for each device on LAN A that needs to communicate with LANs B
and C to have independent routing rules specifying the BU-245U-E clients at B and C as gateways to those networks.
The routing rules for the Access Point in the above example are shown below. The first entry shows the route to LAN B. The gateway for the route
to LAN B is configured as the wireless IP address of the BU-245U-E client connected to LAN B. The destination for the route is configured as the
network address of LAN B. Because the host id of the destination IP address is 0, it specifies a network address. Consequently, any traffic
received at the Access Point with destination IP address 169.254.109.x (where x is any host id) will be forwarded to the BU-245U-E at LAN B.
Devices on LAN B & LAN C that needs to send messages back to LAN A will need to have their Gateway addresses directed to the BU-245U-E on
their respected networks. i.e., a LAN B device needs to send data back to LAN A. The Gateway address will need to be configured as
169.254.109.40 as this is the IP address of the wired side of the LAN B BU-245U-E. Any message coming in with a 192.168.0.X IP address will
be directed across the wireless interface to LAN A.
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