Capturing and decoding network traffic can impose a burden on the resources of your Macintosh. If the network interface is busy, tcpdump may start to drop packets. There are a number of issues that you may need to consider if you find that tcpdump is dropping the packets you actually need:

• Dynamic Display consumes additional CPU resources. Consider turning off Dynamic Display.
• The larger the Packet Capture Size (or “slice”) you ask for, the greater the demands on memory and processing. Consider reducing the Packet Capture Size to the minimum you actually need.
• If the network interface is busy, it is unlikely that you will actually need to capture every single packet. Consider using filters so that tcpdump only captures what you actually need.