ELSA Cable manual

Operating modes and functions 39

KInitially the router checks whether a DNS server has been entered in its own settings (in configuration tool ELSA LANconfig in the 'TCP/IP' configuration section on the 'Addresses' tab or in the /Setup/TCP-IP Module menu). If it finds it there, it will then retrieve the desired information from this server.

KIf no DNS server has been entered in the cable modem, it tries to reach the network operator's DNS server to retrieve the IP address associated with the name. The address of the DNS at the network operator is transferred during the registration of the cable modem by the headend.

This procedure does not require you to have any knowledge of the DNS server address. Entering the LAN IP address of the cable modem as the DNS server for the workstation computers is sufficient to enable name associations. This procedure also automatically updates the address of the DNS server. Your local network always receives the most current information even if, for example, the provider sending the address changes the name of his DNS server or you change to another provider.

Bridging

A bridge connects two or more LANs in such a way that they appear to be a single large network. When bridging via cable modems, the LAN of the cable network operator with the headend is on one side and the LAN of the network participants with the cable modem and the local workstations on the other.

LAN of the cable network ope-	further connected cable	LAN of the user
rator	modems

	MCNS
Headend	Cable TV net-	ELSA MicroLink	Hub
	work	Cable

In the bridge operating mode, the ELSA MicroLink Cable transfers all data to computers without locally assigned MAC addresses, between the local network or another local area network (LAN) or a workstation on one side and the cable network on the other side.

The bridge thus learns on its own which MAC addresses are located on its own network and which are located on the other side. After a very high level of data traffic that occurs during the initial negotiations between the two LANs, the network load drops sharply. When receiving data from the cable network, the bridge in the cable modem uses the MAC addresses to determine whether the data is destined for its own LAN. The bridge will only accept data packets that are addressed to MAC addresses in its LAN.

ELSA MicroLink Cable