Cisco 7960 and 7975 unable to register to server

[Teo7810TSG6]

Hi!  I have three Cisco phones for my tests, a 7960, 7965, and 7975.  The 7965 is OK, but the 7960 and the 7975 can't register.

Is there something special that needs to be done for these phones to register?

When doing a WireShark trace, I noticed that the configuration has "USECALLMANAGER" for some of its values, and the phone seems to be using that literally.

 94  45.110356 192.168.100.9 -> 10.10.20.100 DNS 84  Standard query 0x0023 SRV _sip._udp.USECALLMANAGER
 95  45.288820 10.10.20.100 -> 192.168.100.9 DNS 159  Standard query response 0x0023 No such name SRV _sip._udp.USECALLMANAGER SOA a.root-servers.net
 96  45.291135 192.168.100.9 -> 0.0.0.0      SIP/SDP 835  Request: INVITE sip:1101@USECALLMANAGER | 

If I manually set some of the information, then the phone can work.

Where do I set this information in the server?

[jokearns1 · Accepted solution]

Hi,

Closing off on this thread. I understand that all handsets can now register since VLAN MTU was changed to 1300

Regards,

Joe

[Teo7810TSG6]

How does the VLAN MTU affect the "USECALLMANAGER" in the phone configuration downloaded from the server?  It still downloads this, and if the phone is reset, then I have to manually change the configuration on the phone.