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Some phones on same switch register with Pub and some with Sub.

I have some users outside of our internal router reporting about 30 out of 100 phones are "Registering."

In the CUCM, there are some phones registering to my Publisher and some not registering at all. Most of them are correctly registered with the Subscriber and are working fine. Most of these phones (working and nonworking) are on the same switch, same blades, same subnet/Vlan, switch ports configured the same, configured the same in CUCM, same models and all purchased at the same time.

I have reset my servers (Sub first, Pub second). No change.

Factory reset a phone. Could not pull firmware..

Swapped a good and bad phone with respective ports. No change.

Deleted and reconfigured a bad phone in CUCM. No change

Checked route in the internal router. Correct

Have not checked the user's router. They manage their own network.


From Pub to a phone registered to Pub - Good

From Pub to a phone registered to Sub - Good

From Sub to a phone registered to Sub - Good

From Sub to a phone registered to Pub - Bad

From Sub to all hops routed to the phones in question - Good

It seems as though ONLY a few phones cannot contact my Subscriber which is also the TFTP server. They have yet to check settings on the phones themselves due the restricted settings access. I tried enabled settings access on a phone that was registered to the Pub and it will not take.

This issue is ONLY with devices outside of our internal network.

Please Help!

Bradley Gruesbeck
Cisco Employee


Thanks for the question.

This sounds like you have network issues restricting traffic. I would first check the switch port configuration and verify that the phones are correctly getting the vlan/dhcp/tftp information. I would also try placing a PC on the voice vlan and test connectivity by trying to download the phones tftp file using the command 'tftp get SEP.cnf.xml'.

You would also want to look at collecting packet captures of a phone booting up to find proof of what is going on. That capture will show cdp/dhcp/tftp traffic and will also prove that the phone is trying to make a connection however traffic may not be getting back. I would recommend spanning the network port for the capture (don't try the capture from the back of the phone).

One more thought is to check replication on the CUCM cluster. If replication is not working correctly then the sub node won't let the phone register because its database is missing records. I would recommend a tac case for replication help just in case.

Good luck.

Sent from Cisco Technical Support iPad App



1) As a temporary solution, you can make the local router a tftp source and check if the phones boot up. As all the phones are of the same model, it will not be a problem and you just have to copy the xml file and change option 150.

2) Once it occured to me, one of the layer3 switches in the path was dropping udp packets. It was dropping tftp and sccp packets, and hence phone wont bootup. We rebooted that switch and everything was normal again.

3) ccm ------- router ------ switch ------- phone

verify if you are able to tftp transfer from ccm to switch. Just to make sure that tftp is working fine.

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