CGN and VoIP

Hi All,

My understanding is there might be some difficulties using VoIP devices on a CGN network.

Our Fiber users are hooked up to UBNT EdgeRouters, with a CGN address from a PPPoE server. I've had two instances where a user attempted to use an OOMA VoIP device which gave an indication that it was being blocked by a firewall, specifically UDP 53 and UDP 123. The UBNT device's firewall has nothing blocking that specifically (I don't think).

Has anyone had any luck in this realm?

My lack of understanding of this is probably glowing but I'm hoping there's some solution to this. Let me know if more info is needed. Thank you in advance!