Capture traffic using Wireshark and then import the pcap files into Ostinato; and then generate frames back into the network. In this example I demonstrate how you can capture CDP messages using Wireshark and then generate them using Ostinato .My Full CCNA course is here http://ccnax.com.
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Ostinato – Network Traffic Generator Part 7. Easily create packets for testing in your GNS3 network.

Ostinato is a packet crafter, network traffic generator and analyzer with a friendly GUI. Also a powerful Python API for network test automation. Craft and send packets of several streams with different protocols at different rates. Think of it as “Wireshark in Reverse”.