I feel the same, asterisk can be setup, natd completely and still 
function fine.  No need for having a public ip for it.  SIP providers 
might need some effort to make it work, but iax2 providers, its a snap. =)

good luck.
-brett


Chris Bagnall wrote:
>>>All go right, my PBX is in my LAN and all softphones are in my LAN.
>>>Now I want to setup a public ip address and move the PBX outside my 
>>>LAN
>>>Internet <-> ADSL modem <-+-> m0n0wall <-> LAN
>>>                          |
>>>                         PBX
> 
> 
> Is there a good reason why your PBX needs to be outside your LAN? My
> experience (I've done a few Asterisk + m0n0 deployments at clients' sites)
> has been that it's best to have the Asterisk + SIP phones on the same
> network segment, then port forward or 1:1 NAT (if your ISP has given you
> multiple public IPs) to allow SIP/IAX traffic into your Asterisk server.
> 
> That way you can avoid any messy NAT traversal on the phones, which gives
> you a) less configuration work to do with each phone, b) gives you a wider
> range of SIP devices to work with, and c) means you can set up a TFTP server
> on the Asterisk server to dish out config files to all your phones
> automatically if supported by the phones.
> 
> 
>>Unfortunately, just to 
>>keep you on your toes, telephone manufacturers differ 
>>greately in how you configure them to also be NAT aware. I 
>>can personally recommend any phone made by Snom for ease of 
>>use. Polycom and Cisco take about 10 hours of set up to get 
>>right the first time.
> 
> 
> If you really do want phones that'll do NAT traversal, I can add a
> recommendation for the Grandstream and Sipura phones here.
> 
> In an ideal world, I'd recommend using SIP internally, then IAX externally
> to interconnect with other Asterisk servers at different sites, and for
> integration with IP->PSTN gateways.
> 
> Regards,
> 
> Chris