Which of the following statements is true regarding the CIDR notation 172.20.66.5/19?

The statement that the subnet is 172.20.64.0 is correct because CIDR (Classless Inter-Domain Routing) notation defines the network prefix based on the specified number of bits. The "/19" indicates that the first 19 bits of the IP address are used for the network portion.

To determine the network address from CIDR notation, you convert the IP address into binary. The IP address 172.20.66.5 translates to binary as follows:

• 172 in binary: 10101100

• 20 in binary: 00010100

• 66 in binary: 01000010

• 5 in binary: 00000101

This gives you:

10101100.00010100.01000010.00000101

With a /19 prefix, the first 19 bits (the network portion) determine the network address. For a /19, the significant bits are:

10101100.00010100.01000

The remaining bits (the last 13 bits) are zeroed out to define the subnet itself. The last octet remains unchanged, and combining this back indicates that the subnet address starts from