ELSA LANCOM Business LC-4X00, Руководство пользователя

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Operating modes and functions
ELSA LANCOM Business
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constantly updated and be accessible all over the world at any time. DNS servers holding
long tables containing IP addresses and domain names exist for this purpose.
If a computer calls up a home page from the intranet, it first sends out a DNS request:
”Which IP address belongs to www.domain.com?“ If the router has been specified as the
DNS server in the workstations, the request is handled as follows:
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Initially the router checks whether a DNS server has been entered in its own
settings (in
ELSA LANconfig in the 'TCP/IP' configuration section on the 'Addresses'
tab or in the /
Setup/TCP-IP-module
menu). If it finds one it connects to this
server and retrieves the information required.
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If no DNS server is entered in the router, it will attempt to reach a DNS server over
a PPP connection (e.g. from the Internet provider) to get the IP address assigned to
the name from there. This can only succeed if the address of a DNS server is sent to
the router during PPP negotiation.
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If no connection exists, the default route is established and a search is then carried
out there for the DNS server.
This procedure does not require you to have any knowledge of the DNS server address.
Entering the intranet address of your router as the DNS server for the workstation
computers is sufficient to enable you obtain the name assignment. This procedure also
automatically updates the address of the DNS server. The router 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.
Policy-based routing
Policy-based routing describes a process in which particular data packets are given
preferential treatment. This requires evaluation of a special field within the IP data
packet, known as the Type of Service (TOS) field. This preferential treatment of a number
of data packets can, for example, simplify the configuration of the router via the WAN
when large data volumes are to be transferred simultaneously.
You can find more information on policy based circuit routing in the 'Description of the
menu options'.
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. They also need the addresses of DNS-servers and NBNS-
servers 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.