Most IPv4 Internet accesses are behind NAT (Network Address Translation boxes. While students easily learn how NAT translate packets from TCP connections or UDP (https://beta.computer-networking.info/syllabus/default/protocols/udp.html?highlight=udp) flows, the interactions between NAT and the Internet Control Message Protocol is more complex.

A recent blog post provides a nice discussion of these interactions with code demonstrating how to experiment with NAT on Linux as well as packet traces. This could be the basis for a nice lab for students willing to understand NAT in more details.

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