asterisk users - Mar 2010 - SIP, internet calling, per-peer contexts, and multitenancy

Hi.

I'm trying to set up a bunch of SIP phones to register in various
domains on the local subnets connected to an Asterisk appliance, yet be
able to support Internet SIP calling.

My config looks like this:

[general]
context=INVALID
allowguest=yes
autodomain=no
...
domain=redfish-solutions.com,redfish-internet
...


[internal](!)
type=friend
qualify=50
nat=yes
host=dynamic
canreinvite=no
vmexten=voicemail

[sipura](!)
; nothing for now, add SLA's later

[redfish](!)
context=redfish-internal

[garage_1](internal,sipura,redfish)
callerid=Redfish Solutions <117>
secret=xyzzy
port=5060
mailbox=117 at redfish,1234



the problem is this: if I comment out
"domain=redfish-solutions.com,redfish-internet" in the general
section,
then my internal SIP phones make calls using the desired
redfish-internal domain.  But then outside SIP calls from "guest"
peers
end up being rejected because there's no INVALID context (this is to
prevent me from being hacked).

If I uncomment "domain=redfish-solutions.com,redfish-internet" then
all
my SIP phones end up making calls in that context (redfish-internet)
instead, and are indistinguishable from outside guest calls.

So the question is this:  how do I have SIP phones in the
redfish-solutions.com domain that use an explicitly configured context
when present (and it will always be present), but have a catch-all
wildcard context for guest callers calling into the
redfish-solutions.com domain, i.e. sip:100 at redfish-solutions.com?

Thanks,

-Philip