Ccna routing and Switching Complete Study Guide

3.6  Configure and verify single-homed branch connectivity 

using eBGP IPv4 (limited to peering and route advertisement 

using Network command only)

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The Cisco IOS supports a ton of different wide area network 

(WAN) protocols that help you extend your local LANs to other 

LANs at remote sites. And I don’t think I have to tell you how 

essential information exchange between disparate sites is these days—it’s absolutely vital! But 

even so, it wouldn’t exactly be cost effective or efficient to install your own cable and connect 

all of your company’s remote locations yourself, would it? A much better way to get this done 

is to just lease the existing installations that service providers already have in place.

This is exactly why I’m going to devote most of this chapter to covering the various 

types of connections, technologies, and devices used in today’s WANs.

We’ll also delve into how to implement and configure High-Level Data-Link Control 

(HDLC), and Point-to-Point Protocol (PPP). I’ll describe Point-to-Point Protocol over 

Ethernet (PPPoE), cable, digital subscriber line (DSL), MultiProtocol Label Switching 

(MPLS), and Metro Ethernet plus last mile and long-range WAN technologies. I’ll also 

introduce you to WAN security concepts, tunneling, virtual private networks (VPNs) 

and how to create a tunnel using GRE (Generic Routing Encapsulation). Finally, I’ll close 

the chapter with a discussion on Border Gateway Protocol (BGP) and how to configure 

External BGP.

To find up-to-the-minute updates for this chapter, please see 

www.lammle 

.com/ccna

 or the book’s web page at 

www.sybex.com/go/ccna

.

Introduction to Wide Area Networks

Let’s begin exploring WAN basics by asking, what’s the difference between a wide area 

network (WAN) and a local area network (LAN)? Clearly there’s the distance factor, but 

modern wireless LANs can cover some serious turf, so there’s more to it than that. What 

about bandwidth? Here again, some really big pipes can be had for a price in many places, 

so that’s not it either. What’s the answer we’re looking for?

A major distinction between a WAN and a LAN is that while you generally own a LAN 

infrastructure, you usually lease a WAN infrastructure from a service provider. And to be 

honest, modern technologies even blur this characteristic somewhat, but it still fits neatly 

into the context of Cisco’s exam objectives!

I’ve already talked about the data link that you usually own back when we covered 

Ethernet, so now I’m going to focus on the type you usually don’t own—the kind you 

typically lease from a service provider.

There are several reasons why WANs are necessary in corporate environments today.

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Introduction to Wide Area Networks 

883

LAN technologies provide amazing speeds (10/40/100 Gbps is now common) and at a 

great bang for your buck! But these type of solutions can only work well in relatively small 

geographic areas. You still need WANs in a communications environment because some 

business needs require connections to remote sites for many reasons, including the following:

 

■

People in the regional or branch offices of an organization need to be able to 

communicate and share data.

 

■

Organizations often want to share information with other organizations across large 

distances.

 

■

Employees who travel on company business frequently need to access information that 

resides on their corporate networks.

Here are three major characteristics of WANs:

 

■

WANs generally connect devices that are separated by a broader geographic area than 

a LAN can serve.

 

■

WANs use the services of carriers such as telcos, cable companies, satellite systems, 

and network providers.

 

■

WANs use serial connections of various types to provide access to bandwidth over 

large geographic areas.

The first key to understanding WAN technologies is to be familiar with the different 

WAN topologies, terms, and connection types commonly used by service providers to join 

your LAN networks together. We’ll begin covering these topics now.