Home
>
Software
>
Introduction To ISDN, Part III: PAP

Introduction To ISDN, Part III: PAP

Introduction To ISDN, Part III: Configuring PPP PAP Authentication

Now we know how the ISDN link comes up (interesting traffic), and some scenarios that might cause the link to stay up, we need to look at ISDN authentication schemes. The two methods Cisco certification candidates must be familiar with are PAP and CHAP.

Password Authentication Protocol (PAP) sends the username and password over the ISDN link in clear-text. Sending any passwords over any WAN link in clear-text is generally a bad idea, but it's important to know you have this option.

Regarding both PAP and CHAP, it's a common misunderstanding that each side must authenticate the other. PAP and CHAP both support bidirectional and unidirectional authentication; that is, R1 can authenticate R2 without R2 necessarily authenticating R1. It's more common to use unidirectional authentication in a lab environment than a production network, but keep in mind that bidirectional authentication is an option, not a requirement.

The configurations of PAP and CHAP do have their similarities. For both, you'll configure a username/password combination in global configuration mode. Newcomers to ISDN sometimes put the local router name in for the username; remember that the remote router name is the username.

The only real advantage of PAP over CHAP comes in the password configuration. Since PAP actually sends the password as a whole over the link, the two routers can send different passwords during authentication. The operation of CHAP requires that both routers use the same password, and we'll see why in tomorrow's article.

Under the BRI interface, you'll enter encapsulation ppp and ppp authentication pap. So far, your authentication scheme looks like this:

username R2 password CCNA

Int bri0

encapsulation ppp

ppp authentication pap

PAP requires an extra command at this point. The ppp pap sent-username command is required under the interface, indicating the username and password this router will be sending to the remote router.

Int bri0

encapsulation ppp

ppp authentication pap

ppp pap sent-username R1 password CISCO

I always encourage CCNA and CCNP candidates to use as many debugs as possible when working in their lab, since these commands show us how things work. For any PPP authentication, always run debug ppp negotiation before sending interesting traffic to trigger the call. Watching exactly how PAP and CHAP work give you a much better understanding of what's going on "behind the command", and makes you a stronger candidate and a stronger networking engineer.

Tomorrow, we'll take a look at CHAP, and why routers cannot use the same password on both ends of the link.

Keep studying!

Chris Bryant

CCIE ? #12933

chris@thebryantadvantage.com

About The Author

Chris Bryant, CCIE (TM) #12933, has been active in the Cisco certification community for years. He worked his way up from the CCNA to the CCIE, and knows what CCNA and CCNP candidates need to know to be effective on the job and in the exam room.

He is the owner of chris@thebryantadvantage.com, where he teaches CCNA and CCNP courses to small groups of exam candidates, ensuring they each receive the individual attention they deserve. Classes are offered over the Internet and in person in select cities. Chris has custom-written the Study Guide and Lab Workbook used in each course - no third-party training materials or simulators are used. You're invited to visit our site and check out our CCNA and CCNP courses and study aids, and to sign up for our weekly newsletter written personally by Chris. Chris is always glad to hear from Cisco certification candidates at chris@thebryantadvantage.com

taxi from O'Hare Bismarck .. Lockport Chicago limo O’Hare

In The News:

Experts say hackers who used to focus on Windows operating systems are increasingly targeting Apple IDs as part of a new phishing campaign.

Unitree, a Chinese robotics company that developed a backflipping robot, has now introduced a humanoid robot capable of doing a side flip.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

According to the FBI, cybercriminals are sending extortion letters, threatening to release victims' sensitive information unless a ransom is paid.

FireSat is a satellite project designed to detect and track wildfires early, aiming to detect a fire that's the size of a classroom within 20 minutes.

Tech expert Kurt “CyberGuy" Knutsson reports that researchers have uncovered a Chrome vulnerability used in a cyber espionage campaign.

Preserving voicemails securely on Android: Tech expert Kurt “CyberGuy" Knutsson reveals easy methods to keep memories alive forever.

This phishing kit bypasses 2FA via session hijacking and real-time credential theft. Kurt “CyberGuy" Knutsson offers four ways to stay safe from Astaroth phishing attacks.

Tech expert Kurt “CyberGuy" Knutsson discusses Joby Aviation and Virgin Atlantic planning to launch 200-mph U.K. air taxis linking airports and cities.

Fake Apple virus warnings, security alerts and messages are tactics used to prompt you to call a number or click on a malicious link. The CyberGuy explains how to protect your devices.

The combination of artificial intelligence and neuroscience allows a paralyzed man to manipulate a robotic arm by using his brain to imagine movements.

With the help of artificial intelligence, sophisticated fraud techniques emerging today are virtually undetectable to the untrained eye.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents

If you need to free up space on your Mac, consider deleting duplicate photos in your image library. Apple makes it easy to do, and the CyberGuy explains the process.

Microsoft is discontinuing Skype in May after 22 years of service. Kurt the CyberGuy addresses other options for internet-based phone and video service.

Tron 1, a Chinese company's two-legged robot, is versatile and can walk, roll and pivot, even on rough terrain. Tron 1 stands 33 inches tall and weighs 44 pounds.

Hackers are tricking people into installing password-stealing malware by making them press keyboard shortcuts under the pretense of proving they're not bots.

Saving the voices of loved ones can be a comforting way to keep alive memories. Kurt "the CyberGuy" Knutsson explains how to preserve voicemail messages.

Stay up to date on the latest AI technology advancements and learn about the challenges and opportunities AI presents now and for the future.

The FBI warns that some free online document converters load malware onto people's computers, making their private information vulnerable to attack.

Toyota's compact electric FT-Me is designed to tackle challenges of city living while offering an accessible and eco-friendly transportation solution.

Kurt “CyberGuy" Knutsson says 23andMe's bankruptcy raises data privacy fears: Opt out, download and delete data now.

UBTech and Zeekr unite with AI robot swarms to make car manufacturing faster and smarter. Tech expert Kurt “CyberGuy" Knutsson explains how the process works.

Tech expert Kurt “CyberGuy" Knutsson says Apple's Passwords app had a three-month phishing flaw from iOS 18 to 18.2 patch.

Tech expert Kurt “CyberGuy" Knutsson discusses how this super-small electric mini-truck takes a big step toward production.

Introduction To ISDN, Part III: PAP

Software