Question

Your router has the following IP address on Ethernet: 172.16.2.1/23. Which of the following can be valid host IDs on the LAN interface attached to the router?           

i) 172.16.1.100 ii) 172.16.1.198 iii) 172.16.2.255 iv) 172.16.3.0
1. only (i)
2. (ii) and (iii) only
3. (iii) and (iv) only 
4. None of the above

Answer 1

Correct Answer - Option 3 : (iii) and (iv) only 

Concept:

a.b.c.d/NID

Therefore 23 bits are in NID and only 9 bits for Host id.

Explanation:

Last two byte of IP address is represented in binary

Ethernet: 172.16.2.1/23

Range of IP address: 172.16.0000 00010.0000000 to 172.16.0000011.11111111

Range of IP address: 172.16.2.0 to 172.16.3.255

First and last IP address are reserved

Valid Host IP address: 172.16.2.1 to 172.16.3.254

Statement i: 172.16.1.100

It is not valid since it does not fall in the range

Statement ii: 172.16.1.198

It is not valid since it does not fall in the range

Statement iii: 172.16.2.255

It is valid since it does fall in the valid range

Statement iv: 172.16.3.0

It is valid since it does fall in the valid range

Hence option 3 is the correct answer.

Important Point:

NID stands for network ID.