Error 403 (no RFC1918 IP's allowed) when using Zoiper in 3G mode

0 votes


when I use Zoiper in my WLAN I have no problems to register a German 1&1 VoIP account. But when I register the VoIP account in 3G mode I get the following error message:

Registration failed (No RFC1918 IP'S allowed (403))

I use UDP as protocol and the STUN server of my Internet Provider 1&1.

Any idea?

Thanks and kind regards


asked Sep 29, 2015 in Android by flotux (190 points)  

Hello. Did you report the issue to your provider?

Not yet. I thought that maybe I did a wrong configuration of the Zoiper app.

3 Answers

0 votes
Best answer


with the latest Android version 1.27 of today the problem is solved!

Kind regards


answered Oct 26, 2015 by flotux (190 points)  
selected Oct 26, 2015 by Katina
0 votes

I think this is indeed a configuration issue. Try using STUN or rPort, it might make a difference.

answered Oct 1, 2015 by Joachim (11,490 points)  

I've testded all combinations with/without STUN or remote port but I get either this 403 error or the errormessage: Request Timeout (408)

With the app CSipSimple I am able to login and to call and get called via VoIP. So it must be something with the Zoiper app.

Also with the iOS version of Zoiper I was able to register my VoIP number. Any ideas? :-)

0 votes


I'm also trying to get an German 1&1 VoIP number to put in operation on my iPhone 4 with the latest Zoiper app.
The number is in the router at home *not* activated.

I've also the registering problem. Soemtimes more, sometimes less. In-Calls are (mostly) not routed finally to the app. Out-Calls are nearly always without audio in both directions.

With my Sipgate account everythings works perfectly!

Any hints how to set up Zoiper manually with 1&1?

Thank you and best regards


answered Apr 13, 2016 by Walter Krohe (160 points)  
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