An integrated VoIP phone that seamlessly integrates POTS phones and IP phones is provided. In an embodiment, the integrated VoIP phone includes a Session Initiation Protocol (“SIP”) registrar, a SIP session border control (“SBC”), a SIP proxy, a SIP feature server, a SIP-PSTN gateway, a user interface and VoIP telephony functionality found in traditional VoIP phones. In an embodiment, the integrated VoIP phone includes one or more analog telephone adaptors. Other VoIP entities, such as FXS adaptors, register themselves with the integrated VoIP phone through the SIP SBC. These other entities appear as extensions on the integrated VoIP phone and the outside network will only directly communicated with the integrated VoIP phone.