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I am studying for the CCNA exam and I have this question. "Refer to the exhibit. The networks connected to router R2 have been summarized as 192.168.176.0/21 route and sent to R1. Which two packets destination addresses will R1 forward to R2? 192.168.194.160, 192.168.183.41, 192.168.159.2, 192.168.183.255, 192.168.179.4, 192.168.184.45" The exhibit is not important since it's not showing anything. It would be really helpful if someone could demonstrate the mechanism of the answer. Thanks in advance.

Start by convert the 3rd octet into binary (176, 194, 183, 159, 179, 184) then anding each bit in the 3rd octet up to the 5th bit (which /21).
10110000 = 176
11000010 = 194  This one is a no
10110111 = 183  This one is a yes
10011111 = 159  This one is a no
10110011 = 179  This one is a yes
10111000 = 184  This one is a no

Thank you very much for this.