Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

3rd Party SIP phone to CUCM via SIP Proxy

Hi all,

This is the scenario i'm currently working on :

3rd party SIP phone <--> Internet <--> SIP Proxy <--> LAN <--> CUCM

The SIP proxy basically terminates everything (REGISTER, INVITE, etc), including the RTP stream.

I can register the 3rd party SIP phone to CUCM and in CUCM and  i can see SIP Proxy IP Address as the registered address of the phone.

Calls from the 3rd party SIP phone to internal Cisco or internal 3rd party SIP phone and vice versa work like charm.

The only (fatal) problem is i can only register 1 3rd party SIP phone to CUCM via this SIP proxy.

Since this SIP Proxy always use its internal IP Address and port 5060 (TCP) as its source of registration, CUCM sees multiple registrations for multiple extensions (users) come from a single IP and port, and rejects the second registration request.

It seems that CUCM binds a digest user to an IP address and port, therefore cannot accept multiple registrations from a single IP and port.

Can anyone clarify this?  Or is there any way around this?

I'm using CUCM 8.6.2 and CUCM 9.X (both do not work).



  • IP Telephony
Everyone's tags (1)
New Member

Hi Christian,Where able find

Hi Christian,

Where able find a solution or workaround that would allow multiple 3rd party sip phones to authenticate via sip proxy?  I have a similar setup and would like more information.




New Member

ronin751sc,Can you share the


This widget could not be displayed.