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To earn your Cisco CCNA and CCNP certifications, you have got to master ISDN - and in spite of what some men and women say, there's nonetheless a lot of ISDN out there that needs to be supported.  And when it comes to troubleshooting ISDN, there's a lot to appear at.  Is the correct ISDN switchtype configured? Are the dialer map statements right?  What about the dialer-group and dialer-list commands?  And that is just the commence.

I usually say that all troubleshooting begins at Layer 1, the Physical layer of the OSI model.  The usual strategy 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 great notion to location these test calls prior to configuring the interfaces - that way, you know you've got a valid connection just before beginning the configuration (and there's a lot of config to go along with ISDN!)

To location a test call with out using pings, use the isdn contact interface command.

R1#isdn call 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-five-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 get in touch with down correctly, use isdn disconnect interface.  IOS Assist displays the possibilities with this command.

R1#isdn disconnect interface bri  ?

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

b1   Disconnect the data contact on b1 channel

b2   Disconnect the information get in touch with on b2 channel

R1#isdn disconnect interface bri  all

03:58:36: BR0:1 DDR: disconnecting call

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

03:58:36: %ISDN-6-DISCONNECT: Interface BRI0:1  disconnected from 8358662

R2, contact lasted 20 seconds

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

03:58:36: BR0:1 DDR: disconnecting call

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

I say "properly" because the one point you never want to do to finish an ISDN get in touch with, test or otherwise, is just shut the interface.  Telcos don't like it, and ISDN lab devices like it even much less.  Always let the d-channel do its work and tear the contact down in an orderly style - don't just cut it off by shutting the interface down.SDM Software, Inc.
2100 4th St, #132
San Rafael, CA 94901
(415) 670-9302
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