Operating modes and functions
ELSA LANCOM DSL/10 Office
37
If there is no DNS server in the local network, all locally unknown names will be searched
for using the DEFAULT route. By using a DNS server, it's possible to immediately go to
the correct remote station for all of the names with known IP addresses. In principle, the
DNS server can be a separate computer in the network. However, the following reasons
speak for locating the DNS server directly in the
ELSA LANCOM DSL/10 Office
:
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An
ELSA LANCOM DSL/10 Office
can automatically distribute IP addresses for the
computers in the local network when in DHCP server mode. In other words, the
DHCP server already knows the names and IP addresses of all of the computers in
its own network that were assigned IP addresses via DHCP. With the dynamic
address assignments of a DHCP server, an external DNS server might have
difficulties in keeping the associations between the names and IP addresses
current.
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The DNS server in the
ELSA LANCOM DSL/10 Office
can also be used as an
extremely convenient filter mechanism. Requests for domains can be prohibited
throughout the LAN, for subnetworks, or even for individual computers—simply by
specifying the domain name.
When processing requests for specific names, the DNS server takes advantage of all of
the information available to it:
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First, the DNS server checks whether access to the name is not prohibited by the
filter list. If that is the case, an error message is returned to the requesting
computer stating that access to the address has been denied.
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Next, it searches in its own static DNS table for suitable entries.
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If the address cannot be found in the DNS table, it searches the dynamic DHCP
table. The use of DHCP information can be disabled if required.
If the requested name cannot be found in any of the information sources available to it,
the DNS server sends the request to another server—that of the Internet provider, for
example—using the normal DNS forwarding mechanism, or returns an error message to
the requesting computer.
Setting up the DNS server
The settings for the DNS server can be found in
ELSA LANconfig
in the 'TCP/IP'
configuration section on the 'DNS Server' tab. To set up the DNS server, proceed as
follows:
Switch the DNS server on.
set setup/dns-module/operating on
Enter the domain in which the DNS server is located. The DNS server uses this
domain to determine whether the requested name is located in the LAN. Entering
the domain is optional.
set setup/dns-module/domain yourdomain.com
