How to get a Cisco 7941/7961 Message Indicator light working in asterisk!

I recently had the pleasure of trying to make the message indicator light work in several of our asterisk boxes for our Cisco phones. Chances are you may share the same frustration of trying to get this seemingly simple feature working.

So we will keep it very simple:

First off, I recommend firmware version 8.3.1. It’s the version we use and it seems to have the least bugs out of all the releases for these phones. Most new features seem to cater to Cisco CallManager features more than they do Asterisk, so let’s forget all about any versions after 8.3.1 for now!

Second, you will need to edit SEP$MAC.cnf.cml ($MAC being the mac address of your phone) and find the line that has this key:



You will want to change this to 1. There are more options that allow you to fine-tune this, however, I find this best. 1 will make the envelope blink next to the line that has a new voicemail, and will make that light shine so bright!

Now, we have one more step to make this work properly, which can be done two ways:

  • Edit sip_custom.conf and add the following line:


Save the file, reload asterisk.


  • In FreePBX, click on the tools tab, go into SIP Settings (where you change up the NAT settings) and at the very bottom of the page, put in the above setting in the field for extra SIP options. Save, and reload.

You will almost immediately see a change if you already rebooted the phone, if not, well, reboot your phone!

Now go ahead and leave a voicemail and watch the indicator light up!


Some additional notes: You may notice a strange behavior where your dial tone will blip on and off when you start a new call if you have voicemail. This is intended and set as a default in some configs. If you find this annoying, go ahead and open up your SEP$MAC.cnf.xml file and find the following line:


and change it to 0. Reboot the phone, and the behavior should go away.


If you have any questions or comments, feel free to leave a few comments.

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