User manual

Chapter Three Operation
Page 37 March 2010
that the WI-MOD-9-E must handle, by placing it at the branch level in the network tree. As a
branch, the WI-MOD-9-E needs only pass traffic to devices that are its “leaves”.
There is some overhead in maintaining a network utilizing the Spanning Tree Algorithm. Users
wishing to increase their throughput, at the expense of redundancy should disable Spanning Tree.
3.11 Routing Rules
When a WI-MOD-9-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 PPP) and forwards the frame
appropriately. However, if the IP network address does not match any of its interfaces, the WI-
MOD-9-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 WI-MOD-9-E routers). If more than one “next-hop router” is required, the
WI-MOD-9-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 WI-MOD-9-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 WI-MOD-9-E client/routers as next-hop routers (i.e. gateways) to networks B and
C. Note that devices on LAN A should specify the WI-MOD-9-E Access Point as their default
gateway. An alternative to adding routing rules to the WI-MOD-9-E 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 WI-MOD-9-E clients at B and C as gateways to those networks.