Which CIDR notation corresponds to 255.255.255.192?

Which CIDR notation corresponds to 255.255.255.192?

• A. /24
• B. /26
• C. /28
• D. /30

Answer: (B)

The concept here is converting a dotted-decimal subnet mask to CIDR notation by counting the number of leading 1 bits. For 255.255.255.192, the first three octets are 11111111, contributing 24 ones. The last octet, 192, is 11000000, which adds two more ones. So you have 26 leading ones, giving the CIDR notation /26. That means there are 6 host bits, so the subnet has 64 addresses (62 usable). The other masks correspond to different prefixes: 255.255.255.0 is /24, 255.255.255.240 is /28, and 255.255.255.252 is /30, which are not the same as /26.

The concept here is converting a dotted-decimal subnet mask to CIDR notation by counting the number of leading 1 bits. For 255.255.255.192, the first three octets are 11111111, contributing 24 ones. The last octet, 192, is 11000000, which adds two more ones. So you have 26 leading ones, giving the CIDR notation /26. That means there are 6 host bits, so the subnet has 64 addresses (62 usable). The other masks correspond to different prefixes: 255.255.255.0 is /24, 255.255.255.240 is /28, and 255.255.255.252 is /30, which are not the same as /26.