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


in Android by (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


by (190 points)
selected by
0 votes

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

by (11.5k 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


by (160 points)
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