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Chapter 2: Networking Basics
Why do I need a VPN?
10/100 16-Port VPN Router
A DHCP server can either be a designated PC on the network or another network device, such as the Router. By
default, the Router’s Internet Connection Type is
Obtain an IP automatically
(DHCP).
The PC 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.
For DSL users, many ISPs may require you to log on with a user name and password to gain access to the
Internet. This is a dedicated, high-speed connection type called Point to Point Protocol over Ethernet (PPPoE).
PPPoE is similar to a dial-up connection, but PPPoE does not dial a phone number when establishing a
connection. It also will provide the Router with a dynamic IP address to establish a connection to the Internet.
By default, a DHCP server (on the LAN side) is enabled on the Router. 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 Router,
see the Basic Setup section in “Chapter 6: Setting up and Configuring the Router.”
Why do I need a VPN?
Computer networking provides a flexibility not available when using an archaic, paper-based system. With this
flexibility, however, comes an increased risk in security. This is why firewalls were first introduced. Firewalls
help to protect data inside of a local network. But what do you do once information is sent outside of your local
network, when e-mails are sent to their destination, or when you have to connect to your company's network
when you are out on the road? How is your data protected?
That is when a VPN can help. VPNs are called Virtual Private Networks because they secure data moving outside
of your network as if it were still within that network.
When data is sent out across the Internet from your computer, it is always open to attacks. You may already have
a firewall, which will help protect data moving around or held within your network from being corrupted or
intercepted by entities outside of your network, but once data moves outside of your network -- when you send
data to someone via e-mail or communicate with an individual over the Internet -- the firewall will no longer
protect that data.
At this point, your data becomes open to hackers using a variety of methods to steal not only the data you are
transmitting but also your network login and security data. Some of the most common methods are as follows:
1.
MAC Address Spoofing
Packets transmitted over a network, either your local network or the Internet, are preceded by a packet header.
These packet headers contain both the source and destination information for that packet to transmit efficiently.
NOTE:
Since the Router is a device that connects two
networks, it needs two IP addresses—one for the LAN,
and one for the Internet.
In this User Guide, you’ll see
references to the “Internet IP address” and the “LAN IP
address.”
Since the Router uses NAT technology, the only IP
address that can be seen from the Internet for your
network is the Router’s Internet IP address. However,
even this Internet IP address can be blocked, so that the
Router and network seem invisible to the Internet.
VPN (Virtual Private Network):
A security
measure to protect data as it leaves one
network and goes to another over the Internet.
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6
Chapter 2: Networking Basics
What is a VPN?
10/100 16-Port VPN Router
A hacker can use this information to spoof (or fake) a MAC address allowed on the network. With this spoofed
MAC address, the hacker can also intercept information meant for another user.
2.
Data Sniffing
Data “sniffing” is a method used by hackers to obtain network data as it travels through unsecured networks,
such as the Internet. Tools for just this kind of activity, such as protocol analyzers and network diagnostic tools,
are often built into operating systems and allow the data to be viewed in clear text.
3.
Man in the middle attacks
Once the hacker has either sniffed or spoofed enough information, he can now perform a “man in the middle”
attack. This attack is performed, when data is being transmitted from one network to another, by rerouting the
data to a new destination. Even though the data is not received by its intended recipient, it appears that way to
the person sending the data.
These are only a few of the methods hackers use and they are always developing more. Without the security of
your VPN, your data is constantly open to such attacks as it travels over the Internet. Data travelling over the
Internet will often pass through many different servers around the world before reaching its final destination.
That's a long way to go for unsecured data and this is when a VPN serves its purpose.
What is a VPN?
A VPN, or Virtual Private Network, is a connection between two endpoints - a VPN Router, 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 PCs 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,
telecommuters, and/or professionals on the road (travelers can connect to a VPN Router using any computer with
VPN client software that supports IPSec, such as SSH Sentinel.)
There are two basic ways to create a VPN connection:
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Chapter 2: Networking Basics
What is a VPN?
10/100 16-Port VPN Router
VPN Router to VPN Router
Computer (using VPN client software that supports IPSec) to VPN Router
The VPN Router creates a “tunnel” or channel between two endpoints, so that data transmissions between them
are secure. A computer with VPN client software that supports IPSec can be one of the two endpoints. Any
computer with the built-in IPSec Security Manager (Microsoft 2000 and XP) allows the VPN Router to create a VPN
tunnel using IPSec). Other versions of Microsoft operating systems require additional, third-party VPN client
software applications that support IPSec to be installed.
VPN Router to VPN Router
An example of a VPN Router-to-VPN Router VPN would be as follows. (See Figure 2-1.) At home, a telecommuter
uses his VPN router for his always-on Internet connection. His router is configured with his office's VPN settings.
When he connects to his office's 10/100 16-Port VPN Router, the two routers create a VPN tunnel, encrypting and
decrypting data. As VPNs utilize the Internet, distance is not a factor. Using the VPN, the telecommuter now has a
secure connection to the central office's network, as if his computer were physically connected.
Computer to VPN Router
The following is an example of a computer-to-VPN Router VPN. (See Figure 2-2.) In her hotel room, a traveling
businesswoman dials up her ISP. Her notebook computer has VPN client software that is configured with her
office's VPN settings. She accesses the VPN client software that supports IPSec and connects to the 10/100
16-Port VPN Router at the central office. As VPNs utilize the Internet, distance is not a factor. Using the VPN, the
businesswoman now has a secure connection to the central office's network, as if her computer were physically
connected.
For additional information and instructions about creating your own VPN, please visit Linksys’s website at
www.linksys.com.
Figure 2-2: Computer-to-VPN Router VPN
Figure 2-1: VPN Router-to-VPN Router VPN
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Chapter 3: Getting to Know the Router
The Front Panel
10/100 16-Port VPN Router
Chapter 3: Getting to Know the Router
The Front Panel
The Router’s LEDs, Ethernet ports, and Reset button are located on the front panel of the Router.
LEDs
DIAG
Orange. The
DIAG
LED lights up when the system is not ready. The LED turns off when
the system is ready.
System
Green. The
System
LED lights up when the Router is powered on. When the LED is
flashing, the Router is running a diagnostic test.
LAN/Act (1-13)
Green. Each
LAN/Act
LED serves two purposes. If the LED is continuously lit, the Router
is connected to a device through the corresponding port (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
12, 13). If the LED is flashing, the Router is actively sending or receiving data over that
port.
LAN/Act LEDs 9-13 and Internet/Act LEDs 3-7 represent the dual-function ports, which
can be used as LAN or Internet ports. These are LAN ports 9-13 (white print) or Internet
ports 3-7 (dark print) on the Router’s front panel.
Internet/Act (1-7)
Green. Each
Internet/Act
LED serves two purposes. If the LED is continuously lit, the
Router is connected to an Internet device, such as a cable or DSL modem, through the
corresponding port. If the LED is flashing, the Router is actively sending or receiving
data over that port.
Figure 3-1: Front Panel
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Chapter 3: Getting to Know the Router
The Front Panel
10/100 16-Port VPN Router
Internet/Act LEDs 1 and 2 are labeled Internet because they can be used only as
Internet ports.
DMZ
Orange. The
DMZ
LED serves two purposes. If the LED is continuously lit, the Router is
connected to a DMZ host through the DMZ port. If the LED is flashing, the Router is
actively sending or receiving data over that port.
Ports
1-13 (LAN)
These thirteen
LAN
Ethernet ports connect to network devices, such as PCs, print
servers, or additional switches.
LAN ports 9-13 can also be used as Internet ports.
Internet (1-7)
The seven
Internet
Ethernet ports connect to an Internet device, such as a cable or DSL
modem.
Internet ports 1 and 2 are labeled Internet because they can be used only as Internet
ports. When used as an additional Internet port, it connects to a cable or DSL modem.
Internet ports 3-7 can also be used as LAN ports.
DMZ
The
DMZ
Ethernet port connects to a hub, switch, or public server.
Button
Reset Button
The Reset button can be used in one of two ways:
If the Router is having problems connecting to the Internet, press the Reset button with
a paper clip or a pencil tip for four seconds. This performs a warm reset, similar to
rebooting your PC. You will see the Diag LED flash slowly until the warm reset is
complete.
If you are experiencing extreme problems with the Router and have tried all other
troubleshooting measures, press and hold in the Reset button for ten seconds. This will
restore the factory defaults and clear all of the Router’s settings, such as port range
forwarding entries or a new password. You will see the Diag LED flash quickly until the
factory defaults have been restored.
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