[asterisk-users] NAT keep-alive

[Ugo Bellavance]

Hi,

     On my linksys/sipura phones/ATA, there is a setting called "NAT 
Mapping Enable" and another called "NAT Keep Alive Enable"

These settings must be on in my setup so that my phones/ATA remain 
connected to my * server.  My setup is:

Home LAN - Pfsense (NAT, Dynamic Public IP)- Internet - PFsense (1-to-1 
NAT, Static public IP) - Asterisk server.

I was wondering:

What are doing those parameters?

I looked on my Polycom 330 and I haven't found anything similar... Is 
Linksys the only Mfg that has a similar setting?  The polycom doesn't 
have STUN settings either.  I'm looking to buy some SNOM phones (M3 and 
a wired one), does SNOM phones have something similar?

BTW, are there public STUN servers, or must I have my one to use it?

Regards,

Ugo