Suppose an Ethernet packet represents a TCP acknowledgment; that is, the packet contains an IPv4 header with no options and a 20-byte TCP header but nothing else. Is the IPv4 packet here smaller than the Ethernet minimum packet size, and, if so, by how much? What if the packet is IPv6 with no extension headers?

In newer implementations, repeat ARP queries about a timed-out entry are first sent unicast, in order to reduce broadcast traffic. What would have to happen to create a situation where the repeated unicast query for a given IP address fails, but a follow-up broadcast query for that same IP address succeeds?