Show open TCP and UDP ports

I was asked one time how to show open TCP and UDP ports on Cisco IOS device. In *nix and Windows the command is netstat. Before 12.4(4)T IOS version, the command to show open TCP and UDP ports is show tcp brief all. From 12.4(4)T and later they have added

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Protecting Against Tampered Cisco IOS Software

Cisco Systems added a new feature called digitally signed IOS softwares starting on version 15.0(1)M. This protects against tampered Cisco IOS software distributed over the Internet. If someone downloaded this file and then loaded it on their Cisco devices that supports that image opens their network to attackers. Furthermore, attacker

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