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3.11 Routing Rules
When a RM-240 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 any of its inter-
faces, the RM-240 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 RM-240 routers; and in some cases when WDS router
interfaces are used). If more than one “next-hop router” is required, the RM-240 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 speci-
fied 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 RM-240 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 RM-240 client/routers as next-hop routers
(i.e. gateways) to networks B and C. Note that devices on LAN A should specify the RM-
240 Access Point as their default gateway. An alternative to adding routing rules to the
RM-240 in this example would be for each device on LAN A that needs to communicate
with LANs B and C to independently have routing rules specifying the RM-240 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 RM-240 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 des-
tination IP address is 0, it specifies a network address. Consequently,
any traffic received at the Access Point with destina-
tion IP address 169.254.109.x
(where x is any host id) will be
forwarded to the
RM-240 at LAN B.
The Routing Rules
configuration page can be
accessed by
selecting the
“Routing”
link on any of the configuration web pages.
Up to 30 routing rules may be added to each
RM-240. The table below summarises the
configurable parameters a
routing rule.
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A6C8
&+.#'*)#&%'#&,
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&.'#&+-#%#,'
A6C6
&+.#&+-#%#()
&.'#&+-#%#()