|
[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
|
dsl new york
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
|
Hints and tips when you are searching for dsl new york. Well the first thing to do is type in the exact phrase that you are looking for, but I guess that you already know that seeing that you've just searched for dsl new york and this web page came up.
The biggest tip that I've got is not to bother looking any further. You have already struck the Eldorado of dsl new york information. The leaders of the pack. The holy grail of Internet info on the sometimes not so easy to find subject of dsl new york.
That's not to say you're at that page right now, because our dsl new york site is too new to be the best in the field, or even in the top 10 websites. But the Internet sites that we link to above are the leaders of the pack.
Real Time Media On The Net Index
|
Main Menu
Real Time Media On The Net
Site Map
Affiliate Ads, Links, news, etc.
News for 16-Mar-24 Source: BBC News - Home Allan Little: The year the world changed Source: BBC News - Home Yemen's displaced Source: BBC News - Home Drip dry Source: BBC News - Home Africa's top shots: 16-22 December 2016 Source: BBC News - Home Steam baths and brandy Source: BBC News - Home Bethlehem icons created by artists Source: BBC News - Home David Moyes: Manchester United's great traditions have gone says Sunderland boss Source: BBC News - Home UN votes against Israeli settlements Source: BBC News - Home Arctic heatwave could break records Source: BBC News - Home How to stop social media videos autoplaying
Links
Links
Links
|