Introduction

The Cisco Certified Network Associate Routing & Switching certification exam (200-125 CCNA) tests your knowledge and skills related to a range of networking areas. The areas covered include network fundamentals, LAN switching, IPv4 and IPv6 routing, WAN technologies, infrastructure services, security and network management.

In this article, we will discuss what WAN technologies you need to study to pass your CCNA R&S exam. Beyond CCNA, your understanding of WANs will be useful for higher Cisco certifications and your career in networking.

What Percent of the Exam Covers WAN?

WAN Technologies make up 10 percent of the exam materials published by Cisco. WAN concepts are also mentioned in other areas, including network fundamentals and routing.

What is a WAN?

WAN is an acronym for Wide Area Network. It’s a network with communications, often over large distances and generally operated by a single organization. The organization operating the WAN may be one of two types:

  1. The organization may be active in commerce or industry and have plants or offices at several widely dispersed sites
  2. The principal activity of the organization may be the operation of the WAN. It may be offering network services to other organizations, or directly to members of the public

What WAN Topics are Covered in the Exam?

WAN technologies discussed in CCNA R&S can be broken down into the following areas:

  1. Point-to-Point WANs
  2. Metro Ethernet and MPLS
  3. Internet VPNs
  4. eBGP
  5. Quality of Service

These topics cover everything related to WANs that is included in the official exam published by Cisco.

Point-to-Point WANs

Almost any discussion of WANs for the CCNA R&S certification starts with leased lines. The CCNA R&S uses leased lines as part of larger discussions of network fundamentals and IP routing. It then delves into details by exploring two important serial communication protocols and their configuration:

  1. HDLC
  2. PPP

HDLC

HDLC (High-level Data Link Control) is a bit-oriented synchronous data link protocol used for serial communications. You only need a basic understanding of HDLC concepts. However, you must be able to configure, verify and troubleshoot HDLC for leased lines. HDLC is the default encapsulation on serial interfaces of Cisco routers, and is easy to work with.

PPP

PPP (Point-to-Point Protocol) is another data link protocol that you can use. PPP has more advanced features than HDLC, like authentication. You need to know PPP concepts, including frame format and authentication protocols — namely PAP (Password Authentication Protocol) and CHAP (Challenge Handshake Authentication Protocol). You must also be able to configure and verify PPP on WAN interfaces using local authentication.

You should expect to spend more time studying PPP than HDLC.

Metro Ethernet and MPLS

Metro Ethernet and MPLS (Multiprotocol Label Switching) are two popular WAN technologies today.

Ethernet was created for the LAN (local area network) environment. Metro Ethernet is essentially the usage of Ethernet in the WAN. Once you understand Ethernet in the LAN, it should be easier to learn Ethernet in the WAN aka Metro Ethernet.

MPLS is used by ISPs to offer a variety of network services to business customers. The coverage of MPLS in CCNA R&S is limited to MPLS VPN, which is a Layer 3 WAN service.

The CCNA R&S certification discusses Metro Ethernet and MPLS as a service, in terms of what you receive from the service provider as a business customer. The discussion does not go into details of how the service provider would implement the service inside its network. In other words, you don’t have to concern yourself with the configuration of Metro Ethernet and MPLS. The service provider track of Cisco certifications covers the nuts-and-bolts implementation details.

Internet VPNs

An Internet VPN (virtual private network) uses the Internet, an inexpensive but shared and potentially insecure network, to offer private connectivity between sites. Data is kept private through encryption and other means.

GRE

For CCNA R&S, the discussion of VPNs starts with GRE (Generic Routing Encapsulation). CCNA R&S covers GRE in some detail. Take your time understanding GRE concepts. You should also be comfortable configuring, verifying and troubleshooting GRE tunnels. GRE provides the foundation to learn other VPN technologies.

DMVPN

GRE is a point-to-point technology that is not an ideal solution for connecting many sites. You would need to use DMVPN (Dynamic Multipoint VPN) instead of GRE for building large Internet VPNs. DMVPN is a Cisco technology that utilizes mGRE (Multipoint GRE) and NHRP (Next Hop Reachability Protocol) to establish dynamic multipoint VPNs. The CCNA R&S certification covers high-level DMVPN concepts without touching on configuration.

PPPoE

As discussed earlier, PPP is used to build point-to-point WANs. PPP can be extended using PPPoE (PPP over Ethernet) for use over some types of Internet access links, such as DSL (Digital Subscriber Line). PPPoE keeps all the great features of PPP while transporting PPP inside Ethernet frames through Ethernet interfaces..

External BGP

BGP (Border Gateway Protocol) has only recently found a place on CCNA R&S. Still, only eBGP (External BGP) for IPv4 in single-homed scenarios is covered. eBGP is the use of BGP between an enterprise and an ISP. Single-homed scenarios involve a single connection between the enterprise and the ISP. eBGP configuration and verification is also included, though you are specifically required to know only a handful of configuration and show commands.

Quality of Service

QoS (Quality of Service) refers to techniques used by network devices to manage data packets with the goal of providing better network service. QoS tools are offered on both routers and switches for managing bandwidth, delay, jitter and packet loss.

You should be able to describe basic QoS concepts for your CCNA R&S exam. The actual configuration to implement QoS is not in scope. CCNA R&S discusses the following QoS concepts:

Classification and Marking

Classification and marking, or just marking, classifies each packet based on its contents. It then marks the packet by changing some bits in specific fields of the packet header.

Congestion Management (Queuing)

A network device receives a packet, decides where to forward that packet, and then sends the packet out. At times, the outgoing interface for a packet is already busy sending another packet, so the device keeps the packet in a queue. The packet would sit quietly in the queue until the outgoing interface is free. Congestion-management techniques are used to manage queues that store packets while they wait for their turn to exit an interface.

Shaping and Policing

Shaping and policing are two related QoS techniques that keep the bit rate of data flowing through an interface at or below a configured value. Both shaping and policing monitor the bit rate of data, but use two different techniques to restrict the bit rate. Shaping holds packets in queues and delays transmission, while policing resorts to discarding packets.

Congestion Avoidance

Congestion avoidance is a QoS technique that tries to reduce packet loss by discarding some packets on purpose. This technique works with TCP connections only.

What Should I Focus on Studying?

PPP will require a lot of your focus. You only need a basic understanding of HDLC concepts, but you should expect to spend more time studying PPP. You must know PPPoE concepts very well for your CCNA R&S exam, and be comfortable configuring, verifying and troubleshooting PPPoE. Take your time understanding GRE, and be certain to understand the listed QoS concepts.

Conclusion

This concludes our overview of WAN technologies for the CCNA Routing and Switching certification. We hope you now have a reasonable understanding of what you need to focus on when studying WAN technologies for your CCNA R&S exam. Please see the rest of this series for breakdowns of more core concepts in the CCNA exam.

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