IP Phones unable to register properly

Question

I'm running CCM 4.1(3), currently having a unique situation.
Just deployed 3 IP phones, a 7941, 7902 and ATA-186.
The 7941 works perfectly fine, however the 7902 and ATA were not, they seems to be not able to register with the CCM.
When I brought the 2 problem unit back to my office at level 2, they worked fine, again when I brought them back to level 5, the problem persisted.
All the IP phones are connecting to a CE500 PoE switch, all ports Voice and access vlan are verified. I've also swapped the ports with the working 7941, but to no avail, the CCM still shows the phone as not registerd and the IP address showing level 2 office vlan
I've removed the IP address lease from the level 2 VLAN DHCP service, but still it does not register.
What could be wrong? how to find out what went wrong. The 7941 is working fine, but not the rest at level 5 vlan

Answer 1

Here is how to do a factory reset on 7902
http://www.cisco.com/en/US/partner/products/hw/phones/ps379/products_administration_guide_chapter09186a0080473893.html#wp1020434
FACTORY RESET FOR ATA:
Instructions on how to reset ATA 186 to factory default values
There are two codes to reset the Cisco ATA 186 depending on the software
version.
For software version
- earlier than 2.xx, use code 444
- 2.xx and later, use code 322873738 (FACTRESET)
If the ATA 186 does not seem to reset to the factory default settings,
please check to make sure you have turned OFF the use of TFTP server for
provisioning.
If you use a TFTP server for provisioning, follow ALL the steps below to
reset the Cisco ATA 186 to the factory default settings.
If you do NOT use a TFTP server for provisioning, follow steps 2-5 only to
reset the Cisco ATA 186 to the factory default settings.
1. Unplug the ethernet cable.
2. Pick up the telephone handset
3. Press the function button on top of the ATA
4. Enter: 322873738#* or 444#* (Reset box configuration)
5. Hang-up
6. Pick up the telephone handset
7. Press the function button on top of the ATA
8. Enter: 305# (Disables the use of TFTP)
9. When prompted to enter a value, enter 0#
10. When prompted with the option to save, enter 3.
11. Hang-up
12. Reconnect the ethernet cable
** Extra Reference Links **
http://cco.cisco.com/en/US/products/hw/gatecont/ps514/products_administratio
n_guide_chapter09186a00801e0e0c.html#wp1094880