Who this is for: Offices that use a web filter, DNS filter, or content filter, including ones built into a router or security service.

What goes wrong

Desk phones won't finish setting up or show as offline.
The app can't sign in, or signs in but calls fail.
Some features work and others don't, like calls working but voicemail or video not loading.

Why it happens

DNS is the internet's phone book. It turns a name like app.cannonvoip.com into an address.

DNS and content filters block names they think are risky or off limits. If a filter wrongly blocks one of our server names, or a whole category like "internet telephony", phones and apps can't connect.

How to fix it

Sign in to your filtering service or the router's filter settings.
Check the block log for any name ending in cannonvoip.com.
Add cannonvoip.com and all of its subdomains (often written *.cannonvoip.com) to the allow list.
If the filter blocks categories, make sure categories like VoIP, internet telephony, or communications aren't blocked.
If the filter inspects encrypted traffic (often called SSL or HTTPS inspection), exclude cannonvoip.com from it. Inspection can break the secure connections phones and apps use.
Save and restart the phones.

Notes for common router types

On most home and small office routers, look under Parental Controls, Security, or Web Filtering.
On most business firewalls, look under Web Filter, DNS Filter, Content Filter, or Security Profiles, and add an exception for *.cannonvoip.com.
If the filter is a separate cloud service, add the allow list there. Changes can take a few minutes to apply.

How to tell it worked

The block log no longer shows cannonvoip.com names.
Desk phones show as online in the Cannon VoIP portal and the app signs in.
Run the free Net Checker.

Still having trouble? Contact Cannon VoIP support at 888-973-0515 or support@cannonvoip.com.

More router settings that affect call quality

See all router settings · What makes call quality good or bad