Lancom Systems 821 - Manual (Page 17)

LANCOM 821 ADSL/ISDN – LANCOM 1621 ADSL/ISDN – LANCOM 1711 VPN
̈ Chapter 1: Introduction
17
EN
Connecting a LAN to the Internet does not technically differ from coupling
two LANs. The only difference is that it is not just a handful of computers
behind the Internet provider's router. Instead, it is the net of the networks -
the public Internet.
1.4.1 Bridgehead to the WAN
All routers have at least two connections:
̈
at least one for the LAN
̈ at least one for WAN connections
In addition to LAN connectivity (10/100 Mbps Ethernet), several models also
offer an integrated switch. For the connecting to the WAN, the routers use
ISDN, xDSL/cable or ADSL connectors. Several devices contain additionally a
wireless network card and can thus integrate also stations of WLANs (Wireless
LANs) into the routing.
The router's task is to transfer data from the local network to the target net-
work via a suitable WAN connection. Data is also transferred from the WAN
to the desired recipients in the LAN.
1.4.2 Areas of deployment for routers
Routers are mainly used for the following applications:
̈
Internet access for a LAN (e.g. via DSL or ISDN)
The Internet consists of countless large and small networks that are inter-
connected into the world's largest WAN via routers. The router links all the
workstation computers on your local area network to the global Internet.
Security functions such as IP masquerading protect your LAN against
unauthorized access from outside.
̈
LAN to LAN coupling (via VPN or ISDN)
LAN to LAN coupling links individual LANs to form one large network,
even if this means crossing continents. A typical example: A branch office
is to be connected to the LAN of the headquarters. In principle, you can
connect LANs in two ways:
Not possible with
all LANCOM
devices.
୴
High-speed coupling via VPN
The fastest and most economical LAN to LAN links are possible with
VPN (Virtual Private Network) technology, as VPN uses the Internet as
the basis for its communications. The fast xDSL connection of the
router comes into its own here. The precondition: a VPN gateway with