Why can I sometimes not receive calls or hear the caller?

If your phone is behind a NAT router, then your router could be blocking the incoming calls or the voice stream as it does not recognise them.

To get around this on the Sipura, go to the configuration screen in your web browser and go to Admin, Advanced. For both Ext 1 and Ext 2, set the NAT Mapping Enable and NAT Keep Alive to YES and then save your modifications.

If you find this does not help, try setting the NAT Keep Alive Intvl on the SIP tab to a smaller value.

For other brands, please consult the appropriate documentation for enabling NAT traversal.

More help available from technicians via our online support system.