How to "FIX" SIP 503 -DNS Timeout

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asked Aug 28, 2017 in Windows by cathy02 (120 points)  

1 Answer

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Good afternoon,

Which DNS servers do you use and which voip provider do you use?

Didn't see this errors lately.

Best Regards,


answered Sep 1, 2017 by Zwagerman (3,870 points)  

Hi there. 

I've been using Zoiper for a year now with a Motorola Modem. 

Yesterday it was replaced with a Optical Fiber Alcatel-Lucent modem. 

My Zoiper is not working and I'm going insane!

I have tried to open the ports on the modem, but it seems I am not doing it the right way. 

Can somebody please guide me through how to open ports or configure my PC Zoiper?

The telephone company does not know how to do so. 

Much appreciated. Thanks and have a great day!


Sorry not experience with that particular modem, but please open up tcp/udp port for example 5080 and tell zoiper to use this port or enable the STUN server.

Please have a look here :



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