How to remedy anonymous calls rejected by Lync when using AudioCodes Gateways


by James Young | 11.28.2012
Categories: Blog

When a call comes in from the PSTN with just anonymous for the FROM line

(excerpt from SysLog)

29d:10h:35m:33s INVITE sip:+19528926910@;user=phone SIP/2.0
Via: SIP/2.0/TCP;branch=z9hG4bKac1354670853;alias
Max-Forwards: 70

From: “anonymous” ;tag=1c1354636487

Lync rejects the call and the caller hears a fast busy. To resolve the issue you need to replace the anonymous From line with a valid number. I chose to have 952-555-1212 as the valid number for blocked calls.

In order to replace the number you will need to modify the Source Number Tel->IP Manipulation Table on the gateway (Protocol Configuration – Manipulation Tables – Source Number Tel->IP). The Source Prefix that you will be modifying comes from the phone number that you have assigned to your Trunk Groups (Configuration – Protocol Configuration – Trunk Group – Trunk Group). In my case the numbers are 1100, 1200, 1300 & 1400. You need to make sure that you include all the numbers that can be used. In my case each one is a PRI so that means that the numbers are 1100-1122 ect.

In the manipulation table (Source Number Tel->IP) you need to create a rule for each set of numbers. Destination Prefix will be an asterisk (*) since you want this to affect all incoming numbers. Source Prefix are the numbers that you want it to change. In my case I put in 11[00-22] for the first rule, 12[00-22] for the second and so on. This will only affect the numbers 1100-1122 ect. Leave both Stripped digits columns set to 0 and change the “Prefix to Add” to the number that you want displayed on the Lync client for blocked calls. I chose +19525551212. Leave “Suffix to Add” blank, “Number of Digits to Leave” to 0 and set “Presentation to Allowed. Make sure that you save the changes.

In addition, you will need to change one INI file setting. Go to the IP address of the gateway /AdminPage (Example: On the left Click on “ini Parameters”. In the Parameter Name field put in USESOURCENUMBERASDISPLAYNAME and click on the Apply New Value button. In the output window you should see that the current value is 0. You will want to change this to 1 by putting a 1 in the Enter Value box and clicking on the Apply New Value button.

Burn the configuration to the gateway and you will be able to receive blocked calls from the PSTN to Lync DIDs.