SIP OPTIONS pings are widely used in SIP communications networks as a health check mechanism. You can have your PBX issue SIP OPTIONS messages to a Zentrunk SIP trunk and Zentrunk will return an appropriate response that you can use as an indication of the health of your outbound trunk. This technique can help you avoid trying to set up a call to an unavailable SIP server, which could lead to delays in placing outbound calls.
SIP OPTIONS pings are supported only on sending requests to an outbound trunk URI and not to trunk IP addresses. You should not send more than one SIP OPTIONS message every 10-15 seconds to avoid your requests getting blocked.