Which of the following IP addresses are valid Class B host addresses if a default Class B mask is in use? (Choose two.)
A . 10.6.8.35
B . 133.6.5.4
C . 192.168.5.9
D . 127.0.0.1
E . 190.6.5.4
Answer: BE
Explanation:
The IP addresses 133.6.5.4 and 190.6.5.4 are both valid Class B addresses when a default mask is in use.
The Class B default mask is 255.255.0.0 and the range of valid addresses is 128.0.0.0-191.255.255.255.
The IP address 10.6.8.35 is a Class A address. The Class A default mask is 255.0.0.0 and the range of valid addresses is 1.0.0.0 – 127.255.255.255, with the exception of the range 127.0.0.1 -127.255.255.255, which is reserved and cannot be assigned. The IP address 192.168.5.9 is a Class C address. The Class C default mask is 255.255.255.0 and the range of valid addresses is 192.0.0.0 – 223.255.255.255. The IP address 127.0.0.1 is a Class A address, but it comes from a reserved portion that cannot be assigned.
The range 127.0.0.1 – 127.255.255.255 is used for diagnostics, and although any address in the range will work as a diagnostic address, 127.0.0.1 is known as the loopback address. If you can ping this address, or any address in the 127.0.0.1 – 127.255.255.255 range, then the NIC is working and TCP/IP is installed. The Class A default mask is 255.0.0.0 and the range of valid addresses is 1.0.0.0 – 127.255.255.255, with the exception of the range 127.0.0.1 – 127.255.255.255, which is reserved and cannot be assigned.
