5
Chapter 2: Planning your Network
What is a VPN?
ADSL Gateway with 4-Port Switch
Since you use the Gateway to share your DSL Internet connection, contact your ISP to find out if they have
assigned a static IP address to your account. If so, you will need that static IP address when configuring the
Gateway. You can get that information from your ISP.
Dynamic IP Addresses
A dynamic IP address is automatically assigned to a device on the network, such as computers and print servers.
These IP addresses are called “dynamic” because they are only temporarily assigned to the computer or device.
After a certain time period, they expire and may change. If a computer logs onto the network (or the Internet) and
its dynamic IP address has expired, the DHCP server will automatically assign it a new dynamic IP address.
DHCP (Dynamic Host Configuration Protocol) Servers
Computers and other network devices using dynamic IP addressing are assigned a new IP address by a DHCP
server. The computer or network device obtaining an IP address is called the DHCP client. DHCP frees you from
having to assign IP addresses manually every time a new user is added to your network.
A DHCP server can either be a designated computer on the network or another network device, such as the
Gateway. By default, the Gateway’s DHCP Server function is enabled.
If you already have a DHCP server running on your network, you must disable one of the two DHCP servers. If you
run more than one DHCP server on your network, you will experience network errors, such as conflicting IP
addresses. To disable DHCP on the Gateway, see the DHCP section in “Chapter 5: Configuring the Gateway.”
What is a VPN?
A VPN, or Virtual Private Network, is a connection between two endpoints - a VPN Gateway, for instance - in
different networks that allows private data to be sent securely over a shared or public network, such as the
Internet. This establishes a private network that can send data securely between these two locations or
networks.
This is done by creating a "tunnel". A VPN tunnel connects the two computers or networks and allows data to be
transmitted over the Internet as if it were still within those networks. Not a literal tunnel, it is a connection
secured by encrypting the data sent between the two networks.
VPN was created as a cost-effective alternative to using a private, dedicated, leased line for a private network.
Using industry standard encryption and authentication techniques - IPSec, short for IP Security - the VPN creates
a secure connection that, in effect, operates as if you were directly connected to your local network. Virtual
Private Networking can be used to create secure networks linking a central office with branch offices,
DHCP
: a networking protocol that allows administrators to
assign temporary IP addresses to network computers by
"leasing" an IP address to a user for a limited amount of
time, instead of assigning permanent IP addresses
dsl
: an always-on broadband connection
over traditional phone lines
dynamic ip address
: a temporary IP
address assigned by a DHCP server
encryption
: encoding data transmitted in a network
ip address
: the address used to identify
a computer or device on a network
IPSec
: a VPN protocol used to implement
secure exchange of packets at the IP layer
server
: any computer whose function in a
network is to provide user access to files,
printing, communications, and other services
VPN
: a security measure to protect data as it leaves
one network and goes to another over the Internet
