Find Sporting Goods on eBay
Video and Audio], Broadcasting and podcasting Broadcast On the Net

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

Cisco CCNA Certfication: Introduction to ISDN, Part I

 by: Chris Bryant

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 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 http://www.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 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.

chris@thebryantadvantage.com


directtv

Brodcast On the Net - streaming video, streaming audio, video conferencing, audio
Broadcast On the Net. If you are running a search for video conferencing and are looking for audio streaming or video streaminng and web conferenceing then you have come to the proper place. You can find many of the finest sites with the best conferencing services. Even find video studios or maybe the video talent to produce your program, no matter what you are looking for you can see the best streaming media here.
Brodcast On the Net - streaming video, streaming audio, video conferencing, audio

directtv - high quality sites


When you’re looking for information on buying directtv it can all seem very overwhelming. But don’t worry, because we’ve sorted through all the directtv sites on the internet and have found the very best ones that will get you what you want, how you want it.
We know how important it is to be informed when you’re looking for directtv. Some websites are better than others and will meet your directtv needs in a better fashion.

When you’re looking for a high quality directtv site you know you can rely on, we recommend the above web site. We have taken the hard work out of your directtv shopping and narrowed our list of directtv websites down to only those of the very best.

Knowing you’re getting value for money is very important in buying directtv, so by coming to this web site you can rest with the sound knowledge that you are getting the directtv you paid for.

By buying through our recommend links you can also rest assured your directtv will be of the highest quality. How do we know? Because when we’re shopping for directtv ourselves it’s where we go.

You might wonder why we’re suggesting you click on some outside links rather than stay on our directtv site. Well it’s because we’ve only just put this site up and haven’t yet got it fully operational. Our aim is to be the best site for directtv info on the net, and I’m sure that one day soon we’ll achieve it. So please bookmark us and come back soon. Meanwhile please follow one of the links.

Main Menu
Broadcast On the Net
Site Map

Affiliate Ads, Links, news, etc.

News for 18-Jul-10

Source: BBC News - Home
OBR chief defends his independence

Source: BBC News - Home
Sats 'unreliable and stressful'

Source: BBC News - Home
Thousands stranded as firm fails

Source: BBC News - Home
Proms to begin with Mahler epic

Source: BBC News - Home
British tour operator collapses

Source: BBC News - Home
A peanut butter and bacon cupcake?

Source: BBC News - Home
Malaria-proof mosquito engineered

Source: BBC News - Home
Arrest in sheltered housing death

Source: BBC News - Home
Row over Canada fighter jet order

Source: BBC News - Home
Clinton voices Lockerbie concerns


Links
Links
Links
Google

Kids Meet | Meetings On The Net | Net Meetings | Take Medicine Correctly
Copyright © 2005. Name of Site here. Last Updated: Sunday, 18-Jul-2010 00:01:03 MDT.
Talk On The Net   Present On The Net   Forum On The Net