Home > WAN Tutorial

WAN Tutorial

March 8th, 2016 Go to comments

Unlike LAN which is used effectively in relatively small geographic areas, WAN services help connect networks at a broad geographic distance, from a few to thousands of kilometers. Let’s see the network below, while LANs are used inside buildings like Home, Office, Internet Service Provider (ISP)… WANs are often used to connect between them. By the way, Internet is the largest WAN nowadays.


Because of long distance connection, individuals usually do not own WAN (unlike LAN which they often own it). They do not have the rights to bury a long cable between buildings either. Therefore they hire available network service providers, such as ISPs, cable or telephone companies… in their cities instead. This helps reduce the connection cost very much.

Note: Although we often think about serial connections with copper cables when talking about WAN but nowadays fiber optical cables play an important role in connection at both LAN and WAN. Great bandwidth, great distance, very little signal loss, high speed, security, thin… are very big advantages in the transmission so they are used more and more popular in networking.

WAN Devices & Terminologies

WAN includes many devices and terminologies so you should grasp them. Below are the most popular ones:

+ Router: a device provides internetworking and WAN access interfaces that connect to the provider network
+ Data Terminal Equipment (DTE): Typically, DTE is the router (at the customer side)
+ Data Communications Equipment (DCE): provides a clocking signal used to synchronize data transmission between DCE and DTE devices.
+ Customer Premise Equipment (CPE): devices located at the customer side. CPE often owned by the customer or hired from the WAN provider. In the picture below, the router, LAN switch and two computers in the house are classified as CPE
+ Demarcation Point: the physical point where the public network ends and the private network of a customer begins
+ Local loop: A cable connects the CPE to the nearest exchange or Central Office (CO) of the service provider. In other words, it is the physical link that connects from the demarcation point to the edge of the service provider’s network


+ CSU/DSU: short for Channel Service Unit/Data Service Unit, used on digital lines such as T1, T3 or E1. CSU/DSU provides clocking signal to the customer equipment interface and terminates the channelized transport media to a leased line. As a result, DSU/CSU converts one form of digital format to another digital format. Therefore CSU/DSU terminates a digital local loop. But you will not see CSU/DSU nowadays because most T1 or E1 interfaces on current routers integrate CSU/DSU capabilities

+ Modem: short for Modulator/Demodulator, a Modem is a hardware device that allows a computer to send and receive information over telephone lines by converting digital data into an analog signal used on phone lines, and vice versa. Modem terminates an analog local loop


WAN Layer 2 Protocols

Two important WAN technologies common in enterprise networks today and will be discussed in our tutorial are: Leased lines (or point-to-point link) and Packet-Switching.


Leased line

The two most popular WAN protocols used on leased lines are High-Level Data-Link Control (HDLC) and Point-to-Point Protocol (PPP).

+ High-Level Data-Link Control (HDLC): a point-to-point protocol and it is the default WAN protocol for Cisco routers. Although HDLC is an open standard but each vendor has a proprietary field in their HDLC implementation which makes HDLC a proprietary protocol. Therefore running HDLC between routers from different vendors is not going to work.
+ Point-to-Point Protocol (PPP): it is an open standard and a point-to-point protocol. This is the most popular WAN protocol nowadays used in Dial, xDSL, ISDN, Serial applications. PPP supports both synchronous (like analog phone lines) and asynchronous circuits (such as ISDN or digital links). PPP consists of two subprotocols:
* Link Control Protocol (LCP): set up the link and take care of authentication. After finishing setting up the link, it uses NCP.
* Network Control Protocol (NCP): negotiate optional configuration parameters and facilities for the network layer. In other words, it makes sure IP and other protocols can operate correctly on PPP link

PPP has built-in security mechanisms which are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). While PAP sends password in clear text, CHAP uses encrypted text (called a hash of the password) with a three-way handshake for authentication so CHAP is very secure.


A big advantage of packet-switching over leased line services is we can connect many routers to the packet-switching service using a single serial link on each router. Each router can then communicate with all other routers. A popular type of packet-switching service that you need to grasp in CCNA is Frame-Relay. Asynchronous Transfer Mode (ATM) is another type of packet-switching service but it is out of CCNA scope and we will not discuss it in this tutorial.

+ Frame-Relay: a digital packet-switched service that can run only across synchronous digital connections. Because digital connections have very few errors, it does not perform any error correction or flow control. However, Frame Relay detects errors and drops bad frames. It is up to a higher layer protocol, such as TCP, to resend the dropped information. For more information about this protocol please read our Frame Relay tutorial.

All three protocols above operate at Layer 2 (Data Link Layer) of the OSI Model.

Comments (39) Comments
Comment pages
1 2 2745
  1. @tinku
    March 8th, 2017

    this is very helpful!!

  2. @tinku
    March 8th, 2017

    please give the new dumps for exam….(200-125)

  3. Musa
    April 14th, 2017

    Here is the New 266 Q&As.

    DOWNLOAD Files at below link url

  4. Russ Hurne
    April 18th, 2017

    That is the best search system in the world


  5. Genevive Velega
    April 19th, 2017

    Very smooth blog post . I definitely like your site. Keep it up!


  6. Anonymous
    May 19th, 2017

    Please,Is still the questions in Frame-relay in the new version of ccna 200-125????

  7. Suq Ma Dik
    May 22nd, 2017

    frame relay is not included anymore in ccna 200-125 v3

  8. Kapatid
    August 6th, 2017

    can you send me the latest dumps of Aug 2017 my email is mark.besa02 @ gmail.com

  9. Charice
    August 7th, 2017

    May i please get a tutorial for WAN technologies, MPLS.Leased lines.Metro ethernet,VPN

  10. Anonymous
    August 15th, 2017

    please can someone send me a link to download 200-125 pdf

  11. Yasir Sufyan
    August 22nd, 2017

    hi if anyone have a latest version of ccna dump please send me on my email…
    {email not allowed}

  12. ‘insert dbo.User_Login values (‘noob’,’notasecret’,’true’)–
    August 24th, 2017

    alert (“hack hack hack”)

  13. sharmarke
    August 31st, 2017

    hi please can any one have latest version of ccna dump

  14. Anonymous
    September 13th, 2017

    Hi! If anyone have a latest version of ccna dump please send me willon95@gmail(dot)com

  15. mighty mouse
    September 18th, 2017

    Hi. please send me the latest ccna dumps at {email not allowed}

  16. mighty mouse
    September 18th, 2017

    Hi. please send me the latest ccna dumps at whitey.choco27@gmail(dot)com

  17. JS
    September 19th, 2017

    Please send me 200-125 dumps and .vce to junurajbanshi @ hotmail .com

  18. Satia
    September 25th, 2017


    Please send me latest 200-125 dumps to {email not allowed}


  19. Satia
    September 25th, 2017


    Please send me latest 200-125 dumps to satia _ mas @ yahoo .com


  20. sifat
    October 23rd, 2017

    hey, I am going to sit for ccna exam next month (November ,2017). Can any one kindly give me latest dumps ?

    It will be very helpful for me.
    email add > sifat0617 @ gmail . com

  21. jrler
    October 28th, 2017

    hey, I am going have the exam next month (early december ,2017). Can any one kindly give me latest dumps ?
    It will be very helpful for me. I will be very grateful
    email add > jrleriche (at) gmail . com

    Thnks in advance for your precious help

  22. iratu
    November 8th, 2017

    about to sit for my exam, can someone provide me with the latest dumps please ira217381(at)gmail.com

  23. Dev
    November 8th, 2017

    Hi! If anyone have a latest version of ccna dump please send me {email not allowed}

  24. Dev
    November 8th, 2017

    Hi! If anyone have a latest version of ccna dump please send me. dmousum(at)gmail.com

  25. Anonymous
    November 21st, 2017

    Please email latest ccna dump to bdizzle_187(at)hotmail.com

  26. Khopithan
    December 17th, 2017

    Hi….Guys if you have latest dump to CCNA, please send to this mail – {email not allowed}
    Thak you….

  27. stau
    January 10th, 2018

    please email latest ccna dump to {email not allowed} please or please do so anyone who have it.

  28. banay
    January 17th, 2018

    in the cmd output for the router atlanta why it’s written
    interact address is

  29. Mitesh Mistry
    February 27th, 2018

    Please can someone email me the latest CCNA 200-125 dumps to {mitesh_mistry81(at)yahoo.co.uk} Cheers.

  30. fire13
    May 31st, 2018

    hi guys
    i am wanna take an exam soon (13.06.2018) so can you help me, latest question types, lab, sims, troubleshootings? I’ll be very pleasure and very thankful for any help!
    Thanks a lot !
    My gmail: a(.)taniqulov420(@)gmail(.)com
    pls guys!!!!!!!!!!!!!!

  31. Anonymous
    June 25th, 2018


    Please any one send the latest ccna 200-125 dumps to my email {email not allowed}

    I will be sitting for exam July 2018

  32. Anonymous
    July 1st, 2018

    kindly forward me CCNA dumbs in my mail box Blouis050atgmail.com

  33. Naresh trivedi
    July 5th, 2018

    Hy friends, I just cleared ccna 200-125 and all the questions 98% and all the sims were from 9 tut. Though I bought dumps from cert-bus and lead4 paas, both are under one management, the sims and questions in 9tut pdf files are quite organised and well prepared. Dont waste money in paying anywhere else, just prepare from here. If you want, you can go through the questions at last moment from other dumps, which is not necessary, I had vlan config, acls, eigrp, multilink sims, private ip range question, ip sla was one, thanks 9tut9.

  34. faisal
    August 4th, 2018

    send latest ccna dumbs at adnanfaisalbaig at gmail.com

  35. Sahil
    August 10th, 2018

    Please send me the latest dumps of CCNA in my email {email not allowed}

  36. Erik
    October 15th, 2018

    Very helpful, this tutorial helps me to clear up all of my queries.

  37. Anonymous
    November 2nd, 2018


  38. Ciscology
    January 3rd, 2019

    Thank you alot 9tut

  39. Charles Kristianovich
    May 13th, 2019

    This tutorial was certainly helpful to day the lese. All the Sims were instituted by the 9tut tutorial.

Comment pages
1 2 2745
Add a Comment