ELSA LANCOM Business 6000, Руководство пользователя

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Technical basics
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ELSA LANCOM Business 6000
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EN
When accessing the Internet from the LAN, on the other hand, the router
itself makes the entry in the port and IP address information table.
The table concerned can hold up to 2048 entries, that is it allows 2,048
simultaneous transmissions between the masked and the unmasked
network.
After a specified period of time, the router, however, assumes that the
entry is no longer required and deletes it automatically from the table.
Which protocols are transmitted using IP masquerading?
Naturally, only those which also communicate using ports. Protocols working
without port numbers or using ports above IP in the OSI model cannot be
masked without special treatment.
The current version of router implements masquerading for the following
protocols:
TCP (and all protocols based on it such as FTP, HTTP, etc.)
UDP
ICMP
7.7 DNS forwarding
Names rather than IP addresses are generally used to access a server over
the Internet. Who knows which address is behind 'www.domain.com'? The
DNS server, of course.
DNS stands for D omain N ame S ervice and refers to the assignment of
domain names (such as domain.com) to the corresponding IP addresses. This
information must be 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?”
This request is dealt with as follows if the router is registered as the DNS
server for the workstation computers:
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 is
successful there, it obtains the desired information from this server.