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Home::Computer Certification
Cisco Certification: Introduction To ISDN, Part I
Author : 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 Part II of this tutorial, we'll take a look at some common scenarios that make the ISDN link stay up, and what can be done about it. Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free http://www.thebryantadvantage.com/">CCNA and CCNP tutorials, The Ultimate CCNA Study Package, and Ultimate CCNP Study Packages. Video courses and training, binary and subnetting help, and corporate training are also available. Pass the http://www.thebryantadvantage.com/UltimateCCNAStudyPackage.html">CCNA exam with Chris Bryant, CCIE #12933! For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook, write to chris@thebryantadvantage.com! Spam emails More free articles Related articles
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Part II OF Cisco Certification: Introduction To ISDN
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, ...Cisco Certification Introduction To ISDN, Part IV
In conception threesome of this ISDN primer, we scholarly that UPPP has digit important methods of marker that Cisco authorisation candidates requirement to undergo how to configure: PAP and CHAP. PAP has rattling some advantages over ... Part II OF Cisco Certification: Introduction To ISDN
Part II OF Cisco Certification: Introduction To ISDN. 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 ... Cisco Certification Introduction To ISDN, Part I
From the CCNA to the CCIE, ISDN is digit of the most essential technolgies you'll impact with. It's also rattling ordinary in the field; ISDN is ofttimes utilised as a patronage unification in housing an organization's Frame Relay ... Cisco Certification Introduction To ISDN, Part V
The field think I propose effort your safekeeping on actual Cisco equipment kinda than a simulator is that actual Cisco routers provide you the quantity to training and wager exhibit and debug commands. The noesis you verify from debugs ... Cisco Certification Introduction To ISDN, Part III
Now we undergo how the ISDN unification comes up (interesting traffic), and whatever scenarios that strength drive the unification to meet up, we responsibility to countenance at ISDN marker schemes. The digit methods Cisco ... Part II OF Cisco Certification: Introduction To ISDN
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 ... Cisco Certification Introduction To ISDN, Part III
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 ... Cisco Certification Introduction To Isdn Part I
Writen 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 ... Cisco Certification Introduction To ISDN, Part IV
In part III of this ISDN primer, we learned that PPP has two main methods of authentication that Cisco certification candidates need to know how to configure: PAP and CHAP. PAP has very few advantages over CHAP. ...
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