[asterisk-users] Getting No Antenna bar when behind a NAT

[edward choi]

My Asterisk server is behind a NAT and I have set:
----------------------------------------------------------------------------
externhost="my.server.address"
externrefresh=180

localnet=192.168.0.0/255.255.0.0
localnet=10.0.0.0/255.0.0.0
localnet=172.16.0.0/12

nat=yes
---------------------------------------------------------------------------
in [general] section of sip.conf.

I can make perfect conversation with my friend with the only exception of
both parties being on private ip address.

There can be four situations when a call is established.
1. A and B are not behind NATs
2. A is behind a NAT, but B is not.
3. A is not behind a NAT, but B is.
4. A and B are both behind NATs (different NAT of course).

Among the four situations, 1, 2 and 3 works fine. (I guess externhost and
localnet did the trick)
But situation 4 does not work.

In situation 4:
When I call my friend, I get only one antenna bar with an exclamation mark.
(I am not talking about the iPhone's wifi bar, nor carrier's bar. I am
talking about Softphone's bar). But my friend has no problem with the
antenna bar. And both of us cannot hear anything.
When he calls me, now he gets one antenna bar and an exclamation mark, but
my antenna bar is just fine. And we still don't hear anything.
One time, there was only one time we could hear each other. He called me and
for the first 3~4 seconds, we could hear nothing. But after that we could
hear each other. I don't know how it worked. It was just one random success.
This is really weird. I tried Viber in the same situation and Viber works
just fine every time.
Could anyone give me any plausible explanation for this phenomenon?

Ed
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