Hey @Graham-Jenkins great question, here is what I see about this question/answer:
Based on the networks 10.8.16.0/22 and 10.8.31.0/21, which of the following is the BEST summarized CIDR notation?
A. 10.8.0.0/16 <<The practice exam says this is right (I believe this is wrong)
B. 10.8.0.0/19 << I believe this should be the correct answer
C. 10.8.0.0/20
D. 10.0.0.0/24
the following is true:
00001010 00001000 00010000 00000000 10.8.16.0/22
00001010 00001000 00011111 00000000 10.8.31.0/21
------------------------------------------------
11111111 11111111 11100000 00000000 or /19
Unless the question was asking for a summarization to the network boundary, then:
00001010 00001000 00010000 00000000 10.8.16.0/22
00001010 00001000 00011111 00000000 10.8.31.0/21
------------------------------------------------
11111111 11111111 00000000 00000000 or /16 summarizes the BEST
Base on the context though, /19 is the best choice. I hope this helps!
Best Regards,
Wes Bryan
Knowledge is a road to be traveled upon, not a destination to be reached~~