Testing ISDN links with pings is fine, but there's another way to do it that ensures your basic ISDN link is functioning. Learn all about this method from Chris Bryant, CCIE #12933.
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.
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!
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!)
To place a test call without using pings, use the isdn call interface command.
R1#isdn call interface bri0 8358662
R1#
03:54:43: BR0 DDR: Attempting to dial 8358662
03:54:43: %LINK-3-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-6-CONNECT: Interface BRI0:1 is now connected to 8358662 R2
To tear the test call down correctly, use isdn disconnect interface. IOS Help displays the options with this command.
R1#isdn disconnect interface bri 0 ?
all Disconnect the data call(s) on all b channels
b1 Disconnect the data call on b1 channel
b2 Disconnect the data call on b2 channel
R1#isdn disconnect interface bri 0 all
03:58:36: BR0:1 DDR: disconnecting call
03:58:36: BR0:2 DDR: disconnecting call
03:58:36: %ISDN-6-DISCONNECT: Interface BRI0:1 disconnected from 8358662
R2, call lasted 20 seconds
03:58:36: %LINK-3-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
Cisco CCNA and CCNP Practice Exam Questions: Etherchannels, Network Security, and More!
Let's test your knowledge of Etherchannels, Voice protocols, and other important Cisco certification exam topics with these practice exam questions!
CCNA Security Exam Tutorial: When It's Good To Add Salt
For your CCNA security exam studies, you need to know when to add SALT, and where! Learn these vital details from Chris Bryant, CCIE #12933.
Cisco CCNA And CCNP Practice Exam Questions: Frame Relay, Uplinkfast, And More!
Sharpen your Cisco exam-taking skills with these complimentary CCNA, CCNP, and Security questions! Topics include frame relay, packet filtering, and Uplinkfast.
