Operating modes and functions
ELSA LANCOM DSL/10 Office
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Which protocols can be 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:
K
TCP (and all protocols based on it such as FTP, HTTP etc.)
K
UDP
K
ICMP
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 Domain Name Service 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:
”What IP address belongs to www.domain.com?”
K
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 retrieves the
required information from this server.
This procedure does not require you to have any knowledge of the DNS server address.
This procedure also automatically updates the address of the DNS server. The 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.
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' in the reference section of your manual.
