Find Sporting Goods on eBay
Video and Audio], Broadcasting and podcasting Real Time Media On The Net

[description], Story, any other text you want to use.

Cisco CCNA Certification: Introduction to ISDN, Part I

 by: Chris Bryant, CCIE #12933

From the CCNA to the CCIE, ISDN is one of the most important technolgies you'll work with. It's also very common in the field; ISDN is frequently used as a backup connection in case an organization's Frame Relay connections go down. Therefore, it's important to know ISDN basics not only for your particular exam, but for job success.

ISDN is used between two Cisco routers that have BRI or PRI interfaces. Basically, with ISDN one of the routers places a phone call to the other router. It is vital to understand not only what causes one router to dial another, but what makes the link go down.

Why? Since ISDN is basically a phone call from one router to another, you're getting billed for that phone call -- by the minute. If one of your routers dials another, and never hangs up, the connection can theoretically last for days or weeks. The network manager then receives an astronomical phone bill, which leads to bad things for everyone involved!

Cisco routers use the concept of interesting traffic to decide when one router should call another. By default, there is no interesting traffic, so if you don't define any, the routers will never call each other.

Interesting traffic is defined with the dialer-list command. This command offers many options, so you can tie interesting traffic down not only to what protocols can bring the link up, but what the source, destination, or even port number must be for the line to come up.

One common misconception occurs once that link is up. Interesting traffic is required to bring the link up, but by default, any traffic can then cross the ISDN link.

What makes the link come down? Again, the concept of interesting traffic is used. Cisco routers have an idle-timeout setting for their dialup interfaces. If interesting traffic does not cross the link for the amount of time specified by the idle-timeout, the link comes down.

To summarize: Interesting traffic brings the link up; by default, any traffic can cross the link once it's up; a lack of interesting traffic is what brings the link down.

In tomorrow's article, we'll take a look at some common scenarios that make the ISDN link stay up, and what can be done about it. Keep studying, and I'll see you tomorrow!

Chris Bryant


Cisco Certified Internetwork Expert #12933

About The Author

Chris Bryant, CCIE (TM) #12933, has been active in the Cisco certification community for years. He has written several books that have helped CCNA candidates around the world achieve the coveted CCNA certification, including several concentrating on binary math conversions and subnetting questions that the average CCNA candidate will need to answer on their CCNA exams.

He is the owner of The Bryant Advantage (http://www.thebryantadvantage.com) where he teaches affordable world-class CCNA courses via the Internet. He's proud to have helped CCNA candidates around the world achieve their career goals. Mr. Bryant's books and courses are sold on his site, on eBay, and on several other major Cisco certification sites.

chris@thebryantadvantage.com


audio player

Real Time Media On The Net
This is one of the best resources for information on Real Time Media On The Net you can possibly find. Follow our links to find more information on Real Time Media On The Net. We hope that we have all of the Real Time Media On The Net details that you could need.
Real Time Media On The Net

Well maybe she knows something about audio player and can tell you a bit but, in some cases, her information will probably be incomplete unless she spends a great deal of time on the Internet. Research takes time and we all know that most mothers do not have any extra time. So, we have decided to give you a Mothers Love by providing you with the best audio player resources available.

We have spent many hours scouring the Net for information about audio player and have linked them here for you. Just take a few minutes and click the link below for a great audio player resource.

Main Menu
Real Time Media On The Net
Site Map

Affiliate Ads, Links, news, etc.

News for 26-Oct-25

Source: BBC News - Home
Preserving Mali's rural life

Source: BBC News - Home
Sri Lankan court acquits five men in Tamil MP murder trial

Source: BBC News - Home
Berlin truck attacker Anis Amri killed in Milan

Source: BBC News - Home
Carrie Fisher: Star Wars actress suffers heart attack

Source: BBC News - Home
Syrian girl with severe burns gets life-changing surgery

Source: BBC News - Home
500 years later

Source: BBC News - Home
Rockettes set for Trump inauguration

Source: BBC News - Home
Ken Matheson: Former British Cycling coach says 'culture of fear' exists

Source: BBC News - Home
Israel settlements: Netanyahu snubs 'shameful' UN vote

Source: BBC News - Home
Wedding gift alpaca has 'surprise' baby


Links
Links
Links
Google

Take Medicine Correctly | Broadcast On the Net | Medical Meetings | Law Meet
Copyright © 2005. Name of Site here. Last Updated: Sunday, 26-Oct-2025 00:01:33 MDT.
RX Right!   Medical Newscast   Medical Newscast