To earn your Cisco CCNA and CCNP certifications, you've got to master ISDN - and despite what some people say, there's still a lot of ISDN out there that needs to be supported. And when it comes to troubleshooting ISDN, there's a lot to look at. Is the correct ISDN switchtype configured? Are the dialer map statements correct? What about the dialer-group and dialer-list commands? And that's just the start.
Laptop Battery I always say that all troubleshooting starts at Layer 1, the Physical layer of the OSI model. The usual method of troubleshooting ISDN is sending pings across the link, but the connection can be tested without using pings or even before assigning IP addresses to the BRI interfaces!
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, 12933, is the owner of The Bryant Advantage ( //www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, Ultimate CCNP Study Packages, and CCNA CBT video training. Pass the CCNA exam, BSCI exam, and BCMSN exam with Chris Bryant, 12933!
Thinkpad It's a good idea to place these test calls before configuring the interfaces - that way, you know you've got a valid connection before beginning the configuration (and there's a lot of config to go along with ISDN!)
Before making a major investment into a computer certification, consider the steps that a vendor does or does not make to protect your investment. Computer certifications have helped me tremendously in building my IT career. By asking the right questions, and taking a hard look at your motives and plans before pursuing a given certification, they can do the same for you. Chris Bryant, 12933, is the owner of The Bryant Advantage ( //www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, Ultimate CCNP Study Packages, and CCNA CBT video training. Pass the CCNA exam, BSCI exam, and BCMSN exam with Chris Bryant, 12933!
Microsoft To place a test call without using pings, use the isdn call interface command.
Occasionally, during your CCNA and CCNP studies, you'll run into a term that just doesn't quite make sense to you. (Okay, more than occasionally!) One such term is "reverse telnet". As a Cisco certification candidate, you know that telnet is simply a protocol that allows you to remotely connect to a networking device such as a router or switch. But what is "reverse telnet", CCNP home lab setup
Laptop Computers R1#isdn call interface bri0 8358662
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Laptop Computer R1#
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Desktop Computer 03:54:43: BR0 DDR: Attempting to dial 8358662
Notebooks 03:54:43: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up
Lenovo 03:54:44: BR0:1 DDR: dialer protocol up
Hard Drive 03:54:45: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up
Travelstar 03:54:49: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 8358662 R2
Gateway To tear the test call down correctly, use isdn disconnect interface. IOS Help displays the options with this command.
Laptop Parts R1#isdn disconnect interface bri 0 ?
Software all Disconnect the data call(s) on all b channels
Hard Drives b1 Disconnect the data call on b1 channel
Electronics b2 Disconnect the data call on b2 channel
Canon R1#isdn disconnect interface bri 0 all
Desktop Pc 03:58:36: BR0:1 DDR: disconnecting call
Desktop Computers 03:58:36: BR0:2 DDR: disconnecting call
Think Pad 03:58:36: %ISDN-6-DISCONNECT: Interface BRI0:1 disconnected from 8358662
R2, call lasted 20 seconds
Repair 03:58:36: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down
Data Recovery 03:58:36: BR0:1 DDR: disconnecting call
Cisco 03:58:37: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to down
Keyboard I say "correctly" because the one thing you don't want to do to end an ISDN call, test or otherwise, is just shut the interface. Telcos don't like it, and ISDN lab devices like it even less. Always let the d-channel do its work and tear the call down in an orderly fashion - don't just cut it off by shutting the interface down.
Monitor
Desktop Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (http://www.thebryantadvantage.com), home of free CCNA and CCNP tutorials, The Ultimate CCNA Study Package, Ultimate CCNP Study Packages, and CCNA CBT video training. Pass the CCNA exam ,BSCI exam , and BCMSN exam with Chris Bryant, CCIE #12933!
For a copy of his FREE "How To Pass The CCNA" or "How To Pass The CCNP" ebook and receive a FREE CCNA and CCNP question every day, just visit the website and claim your free copies!
