This video will show you how to use the pktcap-uw tool in ESXi 5.5. It's an enhanced packet capture and analysis tool that can be used in place of the legacy tcpdump-uw tool. The pktcap-uw tool is included by default in ESXi 5.5.
The tcpdump-uw tool can only capture packets/frames at the vmkernel interface level and cannot capture frames at the uplinks, or vSwitch, or virtual port levels. The new pktcap-uw tool allows traffic to be captured at all points within the hypervisor for greater flexibility and improved troubleshooting.
This article provides information on using the pktcap-uw tool for packet capture and analysis.