Technical Tip: Storm of SIP ACK Request send from FortiVoice

[pchee]

Description	This article describes the Telco side feedback saying that the FortiVoice SIP server is sending a lot of ACK requests to the Telco side.
Scope	FortiVoice.
Solution	Perform packet capture by navigating under System -> Network -> Traffic Capture. Select the relevant (Trunk), in this case, it is (PCCW_SIP). Filter set to SIP and start the capture. Perform multiple calls and then stop the capture. Review the pcap and notice that a lot of SIP ACK requests are sent from FortiVoice-500F corresponding to Telco 200OK. Route: <sip:\000\000\000\000\000\000\000\000\000\000\000\000\000:5060;lr> was noticed: This is because DNS was not able to resolve the FDQN put in on the Trunk setting. Navigate under Trunk -> VOIP -> SIP and change the FQDN to IP address to resolve the issue.