4500 reply 403 Forbidden to Cisco 9711 end-point when it sends a REFER for setting up a conf. call

Hi guys.

 

I have a case where we have an access/backbone environment where a 4500 SD node is responding 403 Forbidden to a Cisco 9711 end-point when it sends a REFER while trying to set up a conference call.

 

I have not set anything in particular for the SBC node to manage REFER or conference call as regularly it is not necessary.

 

Base on above statement; Is it a normal behavior the SBC replying  403 Forbidden to such REFER for end-point trying setting up the conference call with such a REFER method?

 

What settings I should modify to have the SBC stop replying the 403 Forbidden message?