To earn your Cisco CCNA and CCNP certifications, you have got to master ISDN - and in spite of what some people say, there's still a lot of ISDN out there that requirements to be supported. And when it comes to troubleshooting ISDN, there is a lot to appear at <a href=“http://twitter.com/sdmsoftware”>group policy administration</a> . Is the appropriate ISDN switchtype configured? Are the dialer map statements correct? What about the dialer-group and dialer-list commands? And that's just the start off.

I often say that all troubleshooting begins at Layer 1, the Physical layer of the OSI model. The usual method of troubleshooting ISDN is sending pings across the hyperlink, but the connection can be tested without using pings or even prior to assigning IP addresses to the BRI interfaces!

It is a excellent concept to location these test calls ahead of configuring the interfaces - that way, you know you have got a valid connection before beginning the configuration (and there is a lot of config to go along with ISDN!)

To spot a test call without employing pings, use the isdn call interface command.

R1#isdn contact interface bri0 8358662

R1#

03:54:43: BR0 DDR: Attempting to dial 8358662

03:54:43: %Link-three-UPDOWN: Interface BRI0:1, changed state to up

03:54:44: BR0:1 DDR: dialer protocol up

03:54:45: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up

03:54:49: %ISDN-six-CONNECT: Interface BRI0:1 is now connected to 8358662 R2

To tear the test call down properly, use isdn disconnect interface <a href=“http://www.yelp.com/biz/sdm-software-san-rafael”>company web site</a> . IOS Help displays the choices with this command.

R1#isdn disconnect interface bri ?

all Disconnect the data call(s) on all b channels

b1 Disconnect the data contact on b1 channel

b2 Disconnect the information call on b2 channel

R1#isdn disconnect interface bri all

03:58:36: BR0:1 DDR: disconnecting get in touch with

03:58:36: BR0:2 DDR: disconnecting contact

03:58:36: %ISDN-six-DISCONNECT: Interface BRI0:1 disconnected from 8358662

R2, get in touch with lasted 20 seconds

03:58:36: %Link-3-UPDOWN: Interface BRI0:1, changed state to down

03:58:36: BR0:1 DDR: disconnecting get in touch with

03:58:37: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to down

I say ” properly” simply because the a single thing you never want to do to finish an ISDN call, test or otherwise, is just shut the interface. Telcos do not like it, and ISDN lab devices like it even significantly less per your request . Always let the d-channel do its work and tear the contact down in an orderly fashion - never just reduce it off by shutting the interface down.SDM Software, Inc. 2100 4th St, #132 San Rafael, CA 94901 (415) 670-9302 http://sdmsoftware.com