What is a SIP-URI?

A SIP-URI is the SIP addressing scheme that communicates who to call via SIP. In other words, a SIP URI is a user’s SIP phone number. The SIP URI resembles an e-mail address and is written in the following format:


SIP-URI = sip:x@y:Port        where x=username and y=host (domain or IP)


Note: If you do not specify a port, the default SIP port will be assumed (5060). This is shown in the first two examples below. If you have changed the default SIP port to something else, then you need to specify it in the SIP-URI (third example below).


  1. sip:joe.bloggs@
  2. sip:support@phonesystem.3cx.com
  3. sip:22444032@phonesystem.3cx.com:6000

The SIP URI scheme has been defined in the RFC 3261 standard. 3CX from C2 Communications uses SIP URIs.