Network looks like this:
- pretty dumb DSL router ( not modem !) - I'm setting it for my parents, that's what they have.
- a linux host running siproxd. Next I'll try with an even smaller box ( an openWRT router ) - to save power.
- One Grandstream box connected to a regular phone
- Android device, with SipDroid.
The firewall is set to forward all UDP and TCP to the linux box - I added a 'custom' rule, I don't want to deal with the dsl router, all real filtering in linux. You can specify the SIP range - 5060 + whatever RTP.
I'm using Gizmo - I like that it's integrated with google voice, relatively easy to set software for most OSes, etc. Well - not so easy to get sound to get gizmo to work on ubuntu with pulseaudio - lot of time wasted there too - I set gizmo to OSS and used "aoss gizmo", this seems to work for me.
One big problem: siproxd can't deal with the 2 identities, i.e. the ascii username and the phone number.
As a rule, I ignore all the gizmo usernames and use only phone numbers. That means email@example.com will not work, neither "call gizmo" in the UI. To dial you must use firstname.lastname@example.org, or "call SIP" in their UI.
On Grandstream - normal registration, with outbound proxy set, no STUN.
On Sipdroid - there is no direct support for proxy, but you can set the "Server" to the IP address of the linux box running siproxd, and than set Domain to proxy01.sipphone.com. Note that older versions of sipdroid don't have the option - just upgrade with latest from market.
So far no problems with the setup - getting my parents to figure out how to dial and where to connect the wires is another story.