Introduction
This document describes the solution to the fast busy signal that you face when you press the Message button on IP Phone to listen to a voicemail.
Symptoms
You get a fast busy signal when you:
- Try to call a Unity Voicemail pilot number
- Press the Message button
You are able to leave a voicemail, log in with visual voicemail and even view the message notification. However, you are not able to retrieve the voicemail when you press the desired button.
Cisco Unified Communications Manager (CUCM) Version 10.5
No. of nodes: 13
Cisco Unity Connection (CUC) Version 10.5
No. of nodes: 2
Problem
CUC rejects calls as it does not support field resource-priority and you get the error "420 Bad Extension" from CUC.
Solution
In CUCM logs you see that CUCM sends an invite to CUC with these parameters:
"Require: resource-priority
Resource-Priority: NndiKorea.0"
It is because of this parameter in invite you get the error "420 Bad Extension" from CUC .
"SIP/2.0 420 Bad Extension
From: "Test Phone 1" <sip:7542481@180.xxx.xxx.67>;tag=8280~c34414c0-9de6-20d9-ab56-051bd0e173b2-37467698
To: <sip:5551000@160.135.4.105>
Via: SIP/2.0/TCP 180.xxx.xxx.67:5060;branch=z9hG4bK9fd443682d
Expires: 180
Call-ID: 84a7f080-79118c6e-2c9-430487a0@180.xxx.xxx.67
CSeq: 101 INVITE
Unsupported: resource-priority
Allow: ACK,BYE,CANCEL,INVITE,NOTIFY,OPTIONS,REFER,REGISTER,SUBSCRIBE
Content-Length: 0"
You face the error, "Unsupported: resource-priority".
Resource Priority is a field that is used with the Multilevel Precedence and Preemption (MLPP) and, CUC does not clearly understand this field.
To remove it, write a Session Initiation Protocol (SIP) normalization script on CUCM to remove the resource priority header from the Invite sent to CUC.
Apply the SIP Normalization Script on the SIP trunks to CUC:
M = {}
function M.outbound_INVITE(msg)
msg:removeHeader("Require")
msg:removeHeader("Resource-Priority")
end
return M
This resolves the issue.
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