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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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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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