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How to fix Auth Fail error problem on 7900 series phones


This shows how to fix an Auth Fail error when a 7900 series phone is attempting to upgrade it's firmware.

When a phone has an older phone load and tries to register with a CUCM that has phone loads higher than 8.5(2), it will fail to upgrade the phone.  You will see it flash auth fail and then quit.  If you factory reset the phone, you can no longer change the phone's settings to point it to an alternate TFTP server.  I had several spare phones on the shelf that had this problem when I tried to put them into service.  Here is how I got those phone back to a working level of code.

This problem is described in the 8.5(3) release notes:

What you will need:


Spare router

Spare switch (PoE if you have it).

TFTP software (Pumpkin works fine).

Download the following files from using your CCO account.

Set up the TFTP server on a PC.

Unzip the files you downloaded from Cisco into the root directory of the TFTP server.

Change the NIC on your PC to a static IP address

On the spare router, configure a DHCP server with the following attributes:



Option 150:

DHCP range: through

Wipe the configuration on the switch (or at least be sure all the ports are on the same VLAN).

Connect the router and the PC to the switch.

Start the TFTP server if it is not already running.

Connect any phone that is having this problem to the switch. If it does not find the TFTP server, do a factory reset on the phone.

After the phone loads the 8.5(2) code and reboots, disconnect it from the spare switch and plug it into your production network. It will then get your normal option 150 settings and find your production CUCM TFTP server. At that point it will download the new (higher) code and be a working phone again

5 Replies 5


I am in a lab with ISR G2 2901 router along with 3560G PoE switch, trying to set up a CUCME/ CME on the router,

I am trying to register a 7965 phone, the error I am getting is Auth Failed on the IP Phone screen while re-cycling then it shows unprovisioned on the IP Phone screen. This IP Phone I am using was earlier registered and fully functional with  CUCM 8.0.

I am just going to try what you have mentioned above about connecting to a router via a switch?

Just need any input from your side, if what you have menioned above regarding Auth Failed also applied to CUCME/CME


The answer has been give you you above, please read and follow it.

You are probably running into the ITL file issue. When you connect to an 8.x CUCM, a certificate is loaded on the phone that prevents you from registering the phone to a different CallManager. You should go into the security settings on the phone and delete the ITL file.

This can be also achieved by doing a Hard factory default Reset by blowing away the flash of the phone completely except the CNU

The code for the total hard reset is: 3491672850*#

So once the flash is blown away, phone is temporarily dead as it shows the black screen.

To recover from the black screen, setup a DHCP server and TFTP server correctly. Phone will search for the DHCP server, if the DHCP server is set correctly it will point to the TFTP server. Keep the firmware file of the phone older than version 8.5 to the TFTP server. Once phone will recover from the temporarily dead condition, it will not stuck into Auth Fail and will register correctly.


You are a legend.  Almost 10 years later this post is still helping folks.  I just used your instructions today to save a 7965 from the junk pile.  Thank you for posting this. 


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