Most of us out there have a copy of Wireshark on our PCs and laptops for troubleshooting problems as well as for learning and figuring out how protocols work. Well, what if you are troubleshooting a problem and you don't happen to have Wireshark installed?
No problems if you are working on the Nexus 7000, wireshark is built in. Now, don't get too excited, it isn't like there is a built-in GUI (yet?). Cisco simply based their Cisco NX-OS Ethanalyzer on the command-line version of wireshark, also known as T-shark. The syntax is very similar to tcpdump in linux, here is an example:
NX7K# ethanalyzer local sniff-interface inband capture-filter "net 10.1.2.0/24 and port 80"
Also, in newer versions of IOS, you can capture traffic locally on the device then tftp it to your desktop to analyze it, very similar to what Pix's could do 10 years ago. Here's a link to a standard capture example.