Elpro Technologies 450U-E Wireless Ethernet Modem & Device Server User Manual
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www.cooperbussmann.com/wirelessresources
Rev Version 1.0.12-Beta7
Master and it initiates all communications. If the communications was being initiated from each end, i.e. a non-polling
system you would need to put a filter list in each modem to allow the communications to be passed from each end.
With this filter configuration Device A will not be able to access Device E, as Device A is not present in the Whitelist in
Modem C.
It is also recommended to add an ARP filter as this would filter out broadcast ARP requests from other devices on the
LAN which would normally be sent over the radio. ARP (Address Resolution Protocol) is a communication protocol used
by Ethernet devices for associating MAC addresses and IP addresses and is a crucial part of normal network
communications. When a device on a LAN wishes to communicate with another device it needs to know the MAC
Address. If the MAC address is not already known or is in its lookup table it will broadcast an ARP request which
subsequently would be passed over the radio if the modems were setup in bridging mode. If this is a small network it may
not matter however in larger systems there can be a considerable amount of broadcast ARP traffic which if sent over the
radio would compromise the reliability of the wireless link.
It should be noted that adding ARP and IP filters will only filter out ARP traffic and IP traffic, any Ethernet traffic that is not
IP will be passed, and this could include Netbios, IPX, PPP, etc. These protocols could be more effectively filtered by
using MAC filtering or configuring the modems in a Router configuration instead of a Bridge.
If an erroneous configuration has prevented all access to the module, SETUP mode may be used to
restore operation.
MAC Address Filter Configuration:
MAC addresses are uniquely assigned to each device and so can be used to permit or deny network access to specific
devices through the use of Blacklists and Whitelists.
In theory, MAC filtering allows a administrators to permit or deny network access to hosts associated with the MAC
address, though in practice there are methods to circumvent this form of access control through address modification.
The MAC filter entry will match only the source MAC address in the packet.
Note: It is important to add the MAC Address of the configuration PC when creating a Whitelist. If the
configuration PC is not on the Whitelist, it will be unable to communicate with the module for further
configuration.
Blacklist will prevent all listed devices from accessing the module and using the
radio link.
Whitelist will allow devices with the MAC addresses listed to communicate with
the module and utilize the radio link. All other devices are blocked.
Add Entry
Add a row to the table of Mac Address filter rules
Delete Entry
Delete the currently selected MAC address filter rule.
Enable
Check to enable the rule.
Mac Address
Enter the desired source MAC Address
Save Changes
Save changes to non-volatile memory (Reset is required to activate)
Save Changes and Reset
Save to non-volatile memory And restart to activate changes
Figure 46 - Filtering Example