[asterisk-users] Help! - Double NAT issue

[Gary Guthary]

Hi folks.

Please don't flame me but I've been googling around for days, read a
tremendous amount, tried everything, and still no go.

This is most definitely a typical newbie question. - I sure hope there's
somebody(s) out there who'll humble themselves to help me out.

I've set up an 'out of the box' basic Asterisk server running on Slackware
Linux. - It basically works fine. - The wife and I are having lots of fun
playing around with all the VOIP phones I'm using to talk to the thing.

Now. - I want to try to take a phone to my office and try to connect from
there. - But I can't. - Sound familiar?

Here's my setup & some scenarios:

|-----------Home-----------------|            |-----OFFICE-------| 
Asterisk box <---->Linksys WRT54G<--->Internet<--->Linksys WRT54G

At home...
Router:                     Linksys WRT54G
Public IP address:          61.25.172.48 (static)
Public Netmask:             255.255.255.128
DNS1:                       220.152.38.233
DNS2:                       220.152.38.201
Internal IP range:          10.0.0.xxx
Internal IP Netmask:        255.255.255.0
Router's internal IP:       10.0.0.1
DMZ Enabled, points to:     10.0.0.12 (Asterisk server)
(see below)
DHCP Enabled, pool starts:  10.0.0.100

Asterisk Server....
IP address:                 10.0.0.12
Netmask:                    255.255.255.0
DNS:                        Same as router's.

Changes made to sip.conf

externip=61.25.172.48
localnet=10.0.0.0/255.255.255.0
nat=yes

FYI - No other changes made to ANY of Asterisk's .conf files. - It's a basic
'vanilla' test box.

At the office...
Router:			   Linksys WRT54G
                           (out of the box config)

Scenarios:

I have a Sipura SPA-1001, Cisco-7940, Cisco-7905, and X-Lite running on my
home PC.

Although I've got DNS servers assigned, I'm not using server.domain names
(IP addresses only). - So I believe DNS is not an issue.

Scenario A. - When the devices are 'pointing' to the Asterisk server's
'internal' IP (10.0.0.12), they all register and work fine.

Scenario B. - If I configurer a phone to use (as a proxy) the home's 'public
IP' (61.25.172.48), it works fine. - This tells me (I believe) that the
phone is going to the router's 'public IP' but since DMZ is turned on, all
the ports are forwarded to the Asterisk box's 'internal' IP (10.0.0.12).

Scenario C. - The problem.......

If I take a device to my office (i.e. the Sipura) and connect it. - It is
configured to 'talk' to my home's 'public IP'. - This thing doesn't even
REGISTER with the Asterisk server. - So I can't even try to make a call.

This is verified (from the office) by being telnet(ted) into my home
Asterisk box and watching it's console.

Anybody have any clue?

If you want to try for yourself, set up a device and try to connect to my
box's 'public IP' (above) and use a username of '60' with a password of
'1234'. - If that works, try extension '1000' and see if you get the
Asterisk box's 'congratulations' message.

I'd be very interested in your results.

Also, if anybody wants to take this off-forum and discuss/help me out, I'll
be greatly thankful. - I have a Broadvoice account and we can even establish
a phonecon.

Thanks VERY MUCH in advance.

Gary Guthary