ELSA Cable manual Automatic address administration with Dhcp, What are the filter options?

40Operating modes and functions

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:

KBroadcast packets: Data directed at all devices accessible in a network (Setup/ Bridge-Module/LAN-config/Broadcast).

KMulticast 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.

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