Identities - SIP Settings(Section): Support broken Registrar
V6 - V10
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If your VoIP provider works only when you turn on „Support broken registrar“ on the phone's web interface, this means your provider does not call your phone the way the phone requested to be called.
What happens is that incoming INVITEs from your VoIP provider do not contain the contact URI which was previously registered by your phone as its contact.
Thus, the phone cannot safely identify the target line of the incoming call. When you compare the URI in the ﬁrst line of the incoming INVITE and the URI in the Contact of the REGISTER, which the phone sends to the registrar of your provider, they will presumably differ. This is what we mean by “broken registrar”. It is as though your provider has sent a letter to an apartment building with the city, the street address, and the house number on it, but without the recipient’s name. When you turn on „Support broken registrar“, the phone tries to ﬁnd the right apartment by guessing, but this guessing will fail when there are two parties with the same name in the building.