Filter
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Operating modes and functions
ELSA MicroLink Cable
40
What are the filter options?
You may not always wish to transfer all data. Much of the data which is bouncing around
in the LAN is of no interest to remote networks or computers. You can thus block transfer
of the following data packets via the bridge:
Broadcast packets: Data directed at all devices accessible in a network (
Setup/
Bridge-Module/LAN-config/Broadcast
).
Multicast packets: Data which is transferred to all devices accessible in a group
(
Setup/Bridge-Module/LAN-config/Multicast
).
Special filter lists which exclude certain addresses from a transmission or only
allow certain addresses can be set up to handle this data. The bridge filters
differentiate here between destination and source addresses. You can first
establish for both address types whether the associated table contains the
addresses to which data is to be transmitted (
Setup/Bridge-Module/LAN-
config/Dest.-address/Filter-type/pos
) or the addresses to be
excluded (
.../Filter-type/neg
). You then enter the MAC addresses to be
filtered into the table itself.
This method of filtering by entering the exact MAC address naturally demands a certain
degree of maintenance effort. Should the addresses change, when a network adapter is
changed for example, the new addresses must be entered to ensure that the bridge
continues to function.
Automatic address administration with DHCP
In order to operate smoothly in a TCP/IP network, all the devices in a local network must
have unique IP addresses.
In addition to the IP addresses, the devices in the LAN also need the addresses of DNSs
as well as that of a default gateway through which the data packets are to be routed from
addresses that are not available locally.
In a smaller network, it is still conceivable that these addresses could be entered
manually in all the computers in the network. In a larger network with many workstation
computers, however, this would simply be too enormous of a task.
In such situations, the DHCP (Dynamic Host Configuration Protocol) is the ideal solution.
Using this protocol, a DHCP server in a TCP/IP-based LAN can dynamically assign the
necessary addresses to the individual stations.