Technical Tip: Not possible to access Zoom, even if port 443 and 80 are allowed with the open policy

[VinayHM]

Description	This article describes how to fix the issue when the application Zoom is not working even though ports 443 and 80 are allowed with the open policy
Scope	FortiGate.
Solution	Allowing ports 443 and 80 and with broad open policy, the Zoom application is still not working and giving the error site is not accessible. if the public IPs were blacklisted, it gives the error site is not accessible. 5 0.034767 10.0.13.37 170.114.52.2 TLSv1.2 385 Client Hello (SNI=zoom.us) 0.000002000 1 0.000000 10.0.13.37 170.114.52.2 TCP 68 49275 → 443 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM 0.000000000 2 0.034254 170.114.52.2 10.0.13.37 TCP 68 443 → 49275 [SYN, ACK] Seq=0 Ack=1 Win=65535 Len=0 MSS=1420 SACK_PERM WS=8192 0.034254000 3 0.034487 10.0.13.37 170.114.52.2 TCP 56 49275 → 443 [ACK] Seq=1 Ack=1 Win=262656 Len=0 0.000233000 4 0.034765 10.0.13.37 170.114.52.2 TCP 1476 49275 → 443 [ACK] Seq=1 Ack=1 Win=262656 Len=1420 [TCP PDU reassembled in 5] 0.000278000 6 0.066191 170.114.52.2 10.0.13.37 TCP 56 443 → 49275 [ACK] Seq=1 Ack=1421 Win=73728 Len=0 0.031424000 7 0.070056 170.114.52.2 10.0.13.37 TCP 56 443 → 49275 [RST] <--- Seq=1 Win=0 Len=0 Solution: Get new IPs from the ISP or get current IPs unblacklisted by Zoom. The process to check the IP block list: https://mxtoolbox.com/blacklists.aspx