Technical Tip: Tracking the real-time traffic data for a specific interface in FortiGate

[tino_p]

Description	This article describes how to track the real-time data for a specific interface in FortiGate. The results will also be compared with the bandwidth graph information in the GUI.
Scope	FortiGate.
Solution	Use the following commands to track the real-time data. For example, in the 'VL11' interface: diagnose debug enable diagnose debug traffic peek VL11 1     <----- '1' means enable. Wait for 1-2 minutes to generate data. diagnose debug traffic peek VL11 0    <----- '0' means disable. diagnose debug disable Sample outputs:   ...   In the above sample: 1748511508: means the timestamp, use Epoch & Unix Timestamp Conversion Tools to convert the timestamp to May 29, 2025 16:38:28 (pm) / GMT+7 <-----The (converted) timestamp needs to match the time shown in the bandwidth widget in the GUI. 82266857405232: means the TX/Transmit data. 1794590813088: means the RX/Receive data. ACV-FW-01 (ACV-EFW) $ VL11: 1748511508 - ( 82266857405232, 1794590813088) ... VL11: 1748511624 - ( 82267472238280, 1794664392424) Time from 1748511624 to 1748511508 is 116 seconds: Tx: 81444965130112 - 81443202316424 = 614,833,048 bytes / 116 = 5,300,284.89 bit/s = 5,05 Mb/s. Rx: 1794664392424 - 1794590813088 = 73,579,336 bytes / 116 = 634,304.62 bit/s = 0.605 Mb/s. At the same time, in the Firewall GUI, continuously collect the statistics of bandwidth on the 'VL11' interface. Sample outputs: from May 29, 2025, 16:38:28 (pm) to May 29, 2025, 16:40:24 (pm).                Collect the statistics of Inbound and Outbound bandwidth, then calculate the average data: Outbound bandwidth is about 4,745 Mb/s and Inbound bandwidth is about 0,56 Mb/s. Compare the calculated results in the 2 above steps, which show that the results in the Firewall GUI and CLI are about the same during the testing time. Inbound bandwidth is about 0,56 Mb/s while Receive/Rx data is about 0.605 Mb/s. Outbound bandwidth is about 4,745 Mb/s  while Transmit/Tx data is about 5,05 Mb/s.