Hello,

I'm using a Cisco ATA SPA112 for VoIP and I don't know why sometimes they fail registration, after being registered for days.
They're connected with a static local IP, I don't have PPPoE on them.
They're are connected to a MK CPE and I can see from Connection tracking that the SPA112, when it fails to register, isn't source natted.
I only have SIP enabled in /ip services and NAT is a masquerade with src-address and out-interface.
What can cause this problem?
Should I use a stun server?