Phone Fail to Register with CUCM

Ok Ive currently got a few phones that are at branch offices, the phones pick up a local dhcp address ok but are not picking up the correct TFTP address.

I'm getting a wierd class A address in TFTP 1 and 2 (different address) that are completely outside of our scope. I ahve no diea where these are coing from.

I can ping the CCUM and can ping the phone from either side.

Anyone got any ideas ?

Find more posts tagged with

Save $250 on 2025 certification boot camps from Infosec!

Book now with code EOY2025

Button

Comments

networker050184

Do you have an option configured in your DHCP pool to give out a TFTP address?

laidbackfreak

networker050184 wrote:

Do you have an option configured in your DHCP pool to give out a TFTP address?

yep got the option 150 configured with the address of the cucm, same as other sites

weird thing is when I was testing this for the pilot they worked no problem

networker050184

Any kind of config files on the phone or TFTP server to override what it pulls from DHCP?

Kind of shooting in the dark here without much information....

laidbackfreak

the phones are brand new out the box, so no configs on there

the tftp server is the cucm and is the only tftp on the estate all our dhcp servers now point to this out of 5 sites so far 2 have registerd ok and 3 failed (one I know why and nothing to do with this problem) the other 2 I'm getting the same odd IP addresses despite the servers being on completely different subnets.

I did wonder if it was something to do with the firmware on the phones ? but havent found anything to confirm\dismiss that yet

Luckycharms

Honestly TFTP and DHCP are very simple protocols. From the sound of your problem I would say its on the DHCP side more then the TFTP side. Simply because you are receiving an incorrect TFTP address rather then a registration problem. Have you erased the initial configuration on the phones? Are there only certain phones in side that subnet / dhcp pool that do not receive the the correct TFTP address or is it all the phones? Are there any other parameters that are incorrect with with the corresponding phones?

Last but still had to ask.
Do you have any other DCHP servers that would be serving that subnet with incorrect information. I would double check all these and make 100% sure that all your setting are correct.

mikej412

Luckycharms wrote:

Last but still had to ask.
Do you have any other DCHP servers that would be serving that subnet with incorrect information. I would double check all these and make 100% sure that all your setting are correct.

+1

Are the class A address you're getting part of a local broadband/wireless ISP range?

You should have DHCP snooping configured on your switches to prevent someone running internet connection sharing on their laptop from hijacking your phones

Life can get interesting with laptop broadband adapters or someone sharing their wireless connection at home -- and bringing the laptop into the office and plugging it into the corporate network.

laidbackfreak

yep im tending toa gree with you .... but due to segregation of duties here im not allowed to look at the servers and check... depsite having to tell the server guys what i need checking...

ill get a sniffer on it later to see if i can see whats going on
the three different sites are "in theory" all configured the same all seperate subnets and but the tftp address that is being picked up by the phones (49.55.50.46) is the same across all 3 subnets
Ive no idea where this is coming from

Netwurk

I know I'm a little late with this answer as the thread is a few weeks old, but did you try manually configuring the network settings on any of the phones? Most (if not all) of the Cisco IP Phones let you do that.

I know that you ultimately want DHCP to do your work for you, but temporarily using the manual settings (to rule out things like DNS problems) can help you troubleshoot.

laidbackfreak

Netwurk wrote: »

I know I'm a little late with this answer as the thread is a few weeks old, but did you try manually configuring the network settings on any of the phones? Most (if not all) of the Cisco IP Phones let you do that.

I know that you ultimately want DHCP to do your work for you, but temporarily using the manual settings (to rule out things like DNS problems) can help you troubleshoot.

this is pretty much what ive had to do. wierd thing is out of 12 sites only 1 will register through dhcp. I've done a trace on one of the others and the info appears to being sent ok although I am getting "UNHANDLED DHCP OPTION CODE " - type but the value and length are correct.

i'm aiming to go to the site that works and do a trace there to see if i can find out what the differnce is.

If i set dhcp on one of the switches on the remote site rather than leaving the server to do the work, the phones register ok.

So i'm guessing something is wierd with the servers, but to confuse matters further when we did the initial testing with the loan kit I had from cisco it all worked fine

in theory nothings has been changed all very strange