Weidmuller Wireless Ethernet Modem & Device Server WI-MOD-E-G/A User Manual
Rev.
2.16
www.weidmuller.com
58
3.18 - Routing
When a WI-MOD-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 WI-MOD-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-E routers; and in some cases when WDS router interfaces are used). If more than one “next-hop router” is required,
the WI-MOD-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-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-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-E Access Point as their default gateway. An alternative to adding
routing rules to the WI-MOD-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 WI-MOD-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 WI-MOD-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 WI-MOD-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 WI-MOD-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
Figure 52 - Routing
