How do I open UDP ports 5060 thru 5070 on my C6900 router/modem?

Netgear has set up a community forum specifically for the Cable Modem products. Most of the people who watch that forum are more likely to have experience with Cable modems and know how to work it better than those of us who follow this router forum. Might be more likely to find someone who has a solution if the question is posted there:
https://community.netgear.com/t5/Cable-Modems-Routers/bd-p/home-cable-modems-routers

https://community.netgear.com/t5/Cable-Modems-Routers/Opening-UDP-ports-5060-thru-5070/td-p/2162301/jump-to/first-unread-message

 

I would review the user manual for this information. Be sure to disable uPnP if you configure port fowarding on the modem.

Maybe some KB articles can be of help:

https://www.netgear.com/search/?col=10&f.category.size=100&f.document_type.size=100&f.live_price.range=[0TO100]&f.live_price.range=[100TO200]&f.live_price.range=[200TO300]&f.live_price.range=[300TO400]&f.live_price.range=[400TO*]&f.model.size=100&f.solutions.size=100&f.topic.size=100&facet.field=model&facet.field=solutions&facet.field=category&facet.field=live_price&facet.field=lang&facet.field=document_type&facet.field=topic&hideproducts=false&page=1&pagesize=10&query=port%20forwarding%20on%20modems&smartsuggestClick=false&sort1=relevance&sortdir1=desc&tabName=faq&trendingClick=false

Please use this link to the main forum product list to review and choose where to make your posts. 
https://community.netgear.com/t5/NETGEAR-Forum/ct-p/en-netgear

Thank you.