While studying for the CCDA exam and attempting to read the CCDA Official Cert Guide Book (4th Edition) back to back completely things sometimes become a bit ‘bookish’ and ‘text-full’. When this happens it’s good to open up Wireshark, download a couple of packets traces from online repositories and see packets flying around here, there and everywhere.
To download sample captures of various protocols the following links are useful:
http://www.netresec.com/?page=PcapFiles (Follow on links)
http://packetlife.net/captures/ ; http://packetlife.net/captures/leech/
Taking a look at the various control plane packet types of protocols being discussed in the book provides added insight into the underlying techniques being used. Wireshark is a great tool and provides time based analysis tools as well.