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Name
A name to describe the routing rule
(Max 32 characters).
Destination
The destination network (or host) IP address (to
specify a network address set the host address to 0.
i.e. for a class C IP address 192.168.0.0 would specify
a destination network, while 192.168.0.16 specifies a
destination host).
Gateway
The IP address of the next-hop router for the specified
destination.
Subnet Mask
The subnet mask for the destination network.
3.12 Wireless Message Filtering
When configured as a Bridge, the RM-240 will transmit all broadcast messages appearing at
its wired Ethernet port. When the RM-240 is configured as a Router, this does not occur.
In many cases, the intended recipient of the broadcast traffic does not lie at the opposite
end of a proposed radio link. Reducing unnecessary broadcast traffic sent over the radio
link, will increase available bandwidth for data. The RM-240 has a filtering feature to help
reduce unnecessary wireless transmissions and enhance security.
The RM-240 may be configured to reject or accept messages to and from certain
Addresses. To accept wireless messages from particular devices a “Whitelist” of
Addresses must be made. Alternatively to reject messages from particular devices, a
“Blacklist” of Addresses must be made. Filtering applies only to messages appearing at the
wired Ethernet port of the configured RM-240.
The Filter comprises of two lists: one of MAC Addresses and another listing IP protocol
details. Each list may be set as either a blacklist (to block traffic for listed devices and
protocols), or as a whitelist (to allow traffic for listed devices and protocols). The Filter
operates on two rules listed below.
1. A Blacklist has priority over a whitelist. Traffic matching detail in a blacklist will be dis-
carded if it also appears in a whitelist.
2. When one or both lists are whitelists, traffic must have matching detail in at least one
of the whitelists for it to be passed. Note that, as this must agree with rule 1 above,
the traffic detail must not match anything in a blacklist, if present, for it to be passed.
When configuring a Whitelist it is important to add the Addresses of all devices connect-
ed to the RM-240 wired Ethernet port, that communicate over the wireless link. It is par-
ticularly important to add the Address of the configuration PC to the Whitelist. Failure
to add this address will prevent the configuration PC from making any further changes
to configuration. Design of the filter may be simplified by monitoring network traffic and
forming a profile of traffic on the wired network. Network Analysis software, such as the
freely available Ethereal program, will list broadcast traffic sent on the network.
For example, Computer B sees the computer D via Ethernet Modems C & E. The
White Filtering requires that at Modem C has computer B in its white list, Modem E has
computer D in its Whitelist. Computer A will be not be able to access Computer D, as
Computer A is not present in the Whitelist in Modem C.
