Software informational articles

Cisco certification: beginning to isdn, part v - software


The major analyze I counsel receiving your hands on real Cisco gear considerably than a simulator is that real Cisco routers give you the accidental to carry out and learn show and debug commands.

The acquaintance you attain from debugs is invaluable. Frankly, it‚??s this acquaintance that puts you above the ‚??average‚?? CCNA who doesn‚??t have that hands-on experience. Examination debugs in achievement also gives you a head start on the CCNP. Since 90 ‚?" 95% of CCNAs go on to pursue the CCNP, it‚??s a great idea to get happening with debugs now.

Don‚??t make the blooper of coming up until you‚??re studying for your CCNP and CCIE to start culture debugs and shows. The work you do for the CCNA is the foundation for all you‚??ll do in the future.

Never, ever, ever attempt debugs on a assembly network. There are debugs that will give you so much in a row that the router essentially becomes overloaded and then locks up. Never custom debugs on a construction network.

It‚??s crucial to know the apposite show and debug instructions for ISDN for more than a few reasons. First, by inspection ISDN in operation, you can see its processes and change for the better appreciate what‚??s going on. Secondly, it‚??s challenging if not awkward to as it should be troubleshoot ISDN exclusive of conscious the appropriate show and debug commands. (It‚??s easy to overlook an ISDN substantiation error just by looking at the configuration, but in a row debug ppp negotiation will cursorily show you where the challenge lies. )

Let‚??s take a look at the ISDN show and debug guidelines that every CCNA and CCNP ought to know.

Show ISDN Status

If you only know one ISDN show command, it‚??s got to be this one. Continually use this charge after configuring your ISDN button type and any basic SPIDs. The appreciation will show you the beat type (and will also show you if you did not configure a alter type), and whether the SPIDs you entered are valid:

R1#show isdn status Global ISDN Switchtype = basic-ni < ISDN button type is appropriately configured. > ISDN BRI0 interface

dsl 0, edge ISDN Switchtype = basic-ni

Layer 1 Status:


Layer 2 Status:



Spid Status:

TEI 91, ces = 1, state = 5(init)

spid1 configured, no LDN, spid1 sent, spid1 valid < SPID 1 is good. >

Endpoint ID Info: epsf = 0, usid = 1, tid = 1

TEI 92, ces = 2, state = 5(init)

spid2 configured, no LDN, spid2 sent, spid2 valid

Endpoint ID Info: epsf = 0, usid = 3, tid = 1

Layer 3 Status:

0 Effective Layer 3 Call(s)

Activated dsl 0 CCBs = 0

The Free Conduct Mask: 0x80000003

Once in a while, you‚??ll get this amount produced from show isdn status:

R2#show isdn status The in progress ISDN Switchtype = basic-ni1 ISDN BRI0 interface

Layer 1 Status:


Layer 2 Status:

Layer 2 NOT Activated

Spid Status:

TEI Not Assigned, ces = 1, state = 3(await establishment)

spid1 configured, no LDN, spid1 NOT sent, spid1 NOT valid

TEI Not Assigned, ces = 2, state = 1(terminal down)

spid2 configured, no LDN, spid2 NOT sent, spid2 NOT valid

Check your in a row configuration, and if the SPIDs look good, basically close the BRI boundary and open it again. Then run show ISDN class again. If you then see ‚??spids are valid‚??, you‚??re ready to proceed. If you still see a idea that the spids are invalid, you‚??ve most apt mistyped the SPID.

Show Access-List

What‚??s this authority got to do with ISDN? Everything.

Remember how the ISDN link comes up in the first place? Appealing traffic. By default, there is no appealing traffic. You classify appealing transfer with the dialer-list and dialer-group commands, AND the access-list command. If you have a badly behaved with your link never appearance up or with it appearance up and staying up, use this charge to see what interchange has been distinct as interesting.

Show Dialer

Another beneficial be in charge to agree on why an ISDN link is advent up and staying up. This authority shows you how many lucrative calls and abortive calls have taken place, what the contemporary idle-timer value is (by default, it‚??s 120 seconds), and most importantly, what the find and destination was for the flow appealing traffic:

R1#show dialer
BRI0 - dialer type = ISDN
Dial Filament Successes Failures Last called Last status
8358662 1 0 00:00:59
0 incoming call(s) have been screened.
0 incoming call(s) cast off for callback.

BRI0:1 - dialer type = ISDN
Idle timer (120 secs), Fast idle timer (20 secs)
Wait for mover (30 secs), Re-enable (15 secs)
Dialer state is data link layer up
Dial reason: ip (s=172. 12. 21. 1, d=172. 12. 21. 2) < s=Source, d=Destination >
Time until disconnect 62 secs
< Idle timer, reset by appealing travel only >
Connected to 8358662 (R2)

Here, you can see that the idle-timer value is at its default, that there are 62 seconds left until the link comes down (unless attractive travel resets the timer), and that the font of the exciting interchange was 172. 12. 21. 1 and the destination is 172. 12. 21. 2. If that destination is the multicast attend to of a routing protocol ‚?" say, 224. 0. 0. 5 for OSPF ‚?" you know what interchange is care the line up.

Show ISDN History

Want to see what calls have been made in the last 15 minutes? Just run this command. It‚??s advantageous if you‚??re under your own steam in to an ISDN troubleshooting job and want to see what calls have been made.

R1#show isdn
history-------------------------------------------------------------------------------- ISDN CALL HISTORY--------------------------------------------------------------------------------History table has a greatest extent of 100 entries. History table data is retained for a greatest of 15 Minutes. --------------------------------------------------------------------------------Call Passion Called Aloof Seconds Seconds Seconds ChargesType Amount . Number Name Used Left Idle Units/Currency-----------------------------------------------------------------------------------------------------------Out 8358662 R2 121 0Out 8358662 R2 121 0-----------------------------------------------------------------------------------------------------

Debug PPP Negotiation

Not only do you need to know this authority for your CCNA and CCNP exams, you MUST know it to be an helpful ISDN troubleshooter.

When PPP substantiation is first configured, it‚??s austere to mistype a password, or fail to remember to configure a ‚??username / password‚?? combination. As a replacement for of frequently appraisal your consecutively configuration to see what the badly behaved is, run debug ppp negotiation and send a ping to bring the line up. You‚??ll at once see where the challenge is.

R2#debug ppp negotiation PPP protocol negotiation debugging is on R2#ping 172. 12. 21. 1

BR0:1 PPP: Phase is AUTHENTICATING, by both < Both routers are authenticating the other with CHAP. > BR0:1 CHAP: O CHALLENGE id 1 len 23 from "R2" < R2 is distribution a challenge to the cold router. O = ‚??outgoing‚??. > BR0:1 CHAP: I CHALLENGE id 1 len 23 from "R1" < A CHAP challenge has come in from R1. I = ‚??incoming‚??> BR0:1 CHAP: O Rejoinder id 1 len 23 from "R2" < R2 is distribution a comeback to the challenge. > BR0:1 CHAP: I Hit id 1 len 4 < A achievement idea has come in , indicating the challenge was fruitfully met. > BR0:1 CHAP: I Comeback id 1 len 23 from "R1" < A comeback to the challenge sent to R1 is now appearance in. > BR0:1 CHAP: O Achievement id 1 len 4 < The challenge was lucratively met by R1, and a achievement idea is sent. >

By mastering these clean ISDN show and debug commands, you become more intense your likelihood of casual the CCNA and CCNP exams greatly, and greatly build up your on-the-job skills.

I counsel you visit www. cisco. com/univercd for more show and debug commands. Culture to negotiate this costly online store will truly help you befall more costly on the job. Every Cisco router and alter command, along with evasion and usage guidelines, can be found on this site. I‚??ll have an clause posted soon to help you learn your way about the site; in the meantime, I urge you to begin adding up this website to your troubleshooting toolkit.

Chris Bryant, CCIE (TM) #12933, has been effective in the Cisco documentation area for years. He has in black and white a number of books that have helped CCNA candidates about the world attain the in demand CCNA certification, together with more than a few concentrating on twofold math conversions and subnetting questions that the be around CCNA aspirant will need to come back with on their CCNA exams.

He is the owner of The Bryant Improvement (http://www. thebryantadvantage. com) where he teaches inexpensive world-class CCNA courses via the Internet, and sells his all the rage Cisco guarantee books. He‚??s proud to have helped CCNA candidates about the world accomplish their career goals. Mr. Bryant‚??s books and courses are sold on his site, on eBay, and on a number of other major Cisco qualifications sites.

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