router

[logistic_guy]

here is the question

Your router has the following IP address on Ethernet0: \(\displaystyle 172.16.2.1/23\). Which of the following can be valid host IDs on the LAN interface attached to the router? (Choose two.)

A. \(\displaystyle 172.16.0.5\)
B. \(\displaystyle 172.16.1.100\)
C. \(\displaystyle 172.16.1.198\)
D. \(\displaystyle 172.16.2.255\)
E. \(\displaystyle 172.16.3.0\)
F. \(\displaystyle 172.16.3.255\)


my attemb
i know this IP \(\displaystyle 172.16.2.1\) belong to class \(\displaystyle B\) and the range of IP addresses in class \(\displaystyle B\) is from \(\displaystyle 128.0.0.0\) to \(\displaystyle 191.255.255.255\)
so all option given is within the range
i'm confusedwhy some IPs is valid and some is invalid

 

[ElizabethWilkinson]

The subnet mask /23 identifies the IP range that belongs to the subnet. Only IPs in the range 172.16.2.0 to 172.16.3.255 are part of this subnet and broadcast addresses ( 172.16.3.255 ) cannot be assigned to hosts. Other IPs are out of range or serve special purposes.