Troubleshooting Exercise: Cisco IP Phone Registration

"My Phone Doesn't Work"

Mrs. Phelps

Probably the most common issue that any voice engineer will encounter is the dreaded report, "my phone isn't working, please help".  If you are currently supporting users then you know what I mean.  If you're lucky, you got a little more information on the initial report than that, but more than likely you'll need to do some digging to get it all.

On the other hand, if you are studying for CCNA Voice or CCNP Voice - you've probably done some reading but may not have any experience trying to deal with this kind of report.

So, this post will be a role-playing social exercise that I hope you enjoy.  I will be the user and answer things to the best of "the user's" knowledge.  I will also answer questions about the environment as though you dispatched a field engineer, if that's necessary.

Scenario:

Report:  [Mrs Phelps]  "I can't make any calls on my phone and I really need it to do my job, I'm getting behind and losing money!  I can't keep using my cell phone all day long!"

So, Mr. and Mrs. Voice Engineer, what do you do now?  (use comments below)

[amyengineer]  I'd start with asking the user what they see on their phone screen. Polite way of asking "does the phone have power?" Does the phone display "configuring IP?" Does the user hear dial-tone when attempting call?


[Mrs. Phelps]  Well, I'm not stupid.  The phone has power, but thanks for asking.

[Mrs. Phelps]  It does not say "configuring IP", whatever that means. 

[Mrs. Phelps]  I can't even try to make a call, I don't see my extension on the phone like I normally do.

[Unknown]  What numbers are you calling when the call fails?  What else?  What else?
Did calls ever work? When did it stop working? What do you hear when the call fails?
When during the call does it fail? Now, hold my beer while I fix this.

[Mrs. Phelps]  I can't make any calls!

[Mrs. Phelps]  "Did calls ever work?"  Seriously?  Why would I report that something is not working if it never worked?     Ok, I'll play along.  Yes, I have previously been able to use this phone to make calls.

[Mrs. Phelps]  It stopped working when I came into work Monday morning (today). 

[Mrs. Phelps]  I already told that other perky girl, "I can't even dial a number!".  The call doesn't fail - it doesn't even start!

[Mrs. Phelps]  Oh, I just realized!  I meant to tell that perky blond girl that the phone says "Phone Not Registered".  Whatever that means.

[amyengineer]  Based on the fact that the extension isn't showing but it doesn't say "Configuring IP" I would go, or send a tech to go, and unplug the phone and plug it back in. I wouldn't have the user do it if I could help it, because you can't trust they'd plug it back in correctly.

If you have to have the user do it, have them use that snazzy cell phone to text a picture of the back of the phone to you before they unplug it and after.

If this didn't correct the issue, I would reset the phone to factory defaults. Based on my experience, this almost always clears up that particular issue, which I have seen many times.

[Mrs. Phelps]  I can follow simple instructions.  Geez, you folks really think I'm an idiot.   I unplugged everything and plugged it back in.  Looks the same to me.  Here's a photo of the phone, since you can't trust me.  By the way, don't you have anyway to do this remotely?  Sure seems silly if you need to go driving around all the time.

Back of Mrs. Phelp's phone

[Mrs. Phelps]  How much longer is this going to be broken?  What am I paying you for?!

[amyengineer]  Just saw the part about seeing a "Phone Not Registered" message - odd, I've never seen that message - a Registration Rejected message - now *that* I've seen...

[Mrs. Phelps]  That really encourages me.  Perhaps your beer-swiling friend has seen it.  I sent you a photo below since you can't seem to believe me.  Are you always so distrusting?

[Mrs. Phelps]  I'm really getting frustrated now.  The other 20 people in my new office are working fine.  They told us it would be just like the old office, but at this point I wish that I could go back there.

[Mrs. Phelps]  Why are their phones working?

Phone Not Registered

[amyengineer]  I would swap her phone with another phone that is known to be working. If it comes up fine, I would set her up with a spare phone and bring the busted one back for further inspection. Or, alternatively, one could plug her phone into the jack a phone that is working and registered.

If the known good phone does register or if her phone registers at the other wall jack - I would check the following: cable - swap for known good cable from phone to wall. swap cable at switch port to patch panel. Switch port - is port in correct vlan? Are there errors on the port? Is it in an err-disabled state?

Can I ping call manager from the switch?
Is the phone getting a DCHP address in the correct vlan?
What is the option 150? Is it correct?
Is it pingable from the switch?

Check Call Manager, did someone delete the phone? Is the Mac address correct? Can Call Manager ping the endpoints IP address?

[Mrs. Phelps]  I took my phone to Mr. Bigelow's office and it works fine there, but he refuses to let me work in there with him.  He says that my perfume makes him sneeze.  It's a lovely floral scent, but that old fogey wouldn't know a good thing if it hit him in the face.

[Mrs. Phelps]  I'm back in my office now, and it still doesn't work.  Sigh.  Same thing again.  I tried to get Mr. Bigelow to trade offices with me, but his phone doesn't work in my office either.

[Mrs. Phelps]  Is it in a correct vlan?  What is that?  Some kind of gang?

Happy Customer

[Narrator]  The end of our story is nigh. After finally receiving this last bit of information, our illustrious team of voice engineers decides to look at the switch configuration.  After tracing the cable to the switch, it was found to be in a port described to be for a printer - NOT one for a phone.  Hence, the phone was indeed in the wrong vlan.  It was getting an IP address via DHCP, but not from the a DHCP scope within the voice vlan.



Hopefully this exercise has illustrated the importance of asking the right questions during the interview process with the user.  The user has no idea what information you need to know in most cases.  They have no idea what is important and what is not.  A strong understanding of the IP Phone registration process will help target your questions as you go. 

Additional Resources
IP Phone Registration Process
Troubleshooting Cisco IP Phone Registration Problems