VoIP and IPFW

[Gary Corcoran]

Maksim Yevmenkin wrote:

> Hello,
> 
>> I'm considering testing the Vonage service, with my FreeBSD-4.10
>> system (maybe 5 or 6). I wonder if anyone here has a configuration
>> they can share, or if there are any pages out there that detail the
>> proper (and secure) setup.
> 
> 
> i'm using lingo (www.lingo.com) - very similar to vonage. i use freebsd 
> 4.10 as my firewall/nat/wireless access point/etc. the lingo box in 
> behind freebsd box. it gets its ip (local) via dhcp and then talks to 
> the lingo servers (via nat). it seems both providers are using sip, so i 
> did not have to open anything on my nat/firewall, because the lingo box 
> initiates the connection from the inside.

I can understand how you can do outgoing calls behind a NAT firewall,
because you initiate the connection.  But can you receive *incoming*
calls?  Or are you always "connected" to the VOIP provider, and thus
your firewall/reverse-nat is always open/setup?

Thanks,
Gary