A large number of consecutive IP address are available starting at 198.16.0.0. Suppose that four organizations, A, B, C and D request 4000, 2000, 4000, and 8000 address, respectively, and in that order. For each of these, I need to give the first IP address assigned, the last IP address assigned, and the mask int the w.x.y.z/s notation. Please explain for each organization.
Answer
I'm going to keep it short. You should learn the basics of subnetting by Googling for information, I can suggest Cisco for excellent learning material. Your network, 198.16.0.0 /16, offers you 16 bits to use as subnet/host bits. This entire network offers a bit more than 65.000 hosts.
Step 1 - Sort your subnets, starting with the subnet requiring the most amount of hosts. 8000, 4000, 4000, 2000
Step 2 - How many host bits do you need for 8000 usable hosts? 13 host bits: 2^13 = 8192 hosts - 2 = 8190 usable hosts
Step 3 - We know we need 3 subnet bits, so we can add 3 towards the 16. Our new subnet mask for this subnet is /19. Now we'll need to use binaries to figure out the complete first subnet. All zeroes in the host part gives you the network id and all ones in the host part gives you the broadcast id.
198.16.000|00000.00000000 = 198.16.0.0
198.16.000|11111.11111111 = 198.16.31.255
Step 4 - Your subnet for Organisation with 8000 usable hosts is 198.16.0.0/19.
Network ID: 198.16.0.0
First usable host: 198.16.0.1
Last usable host: 198.16.31.254
Broadcast ID: 198.16.31.255
Now we repeat those steps for the remaining 3 Organisations.
Step 1 - We know our next subnet needs to support 4000 usable hosts.
Step 2 - How many host bits do you need for 4000 usable hosts? 12 host bits: 2^12 = 4096 hosts - 2 = 4094 usable hosts
Step 3 - We know we need 4 subnet bits, so we can add 4 towards the 16. Our new subnet mask for this subnet is /20. Now we'll need to use binaries to figure out the complete first subnet. All zeroes in the host part gives you the network id and all ones in the host part gives you the broadcast id. Because we have already subnetted the network, we start where we ended.
198.16.0010|0000.00000000 = 198.16.32.0
198.16.0010|1111.11111111 = 198.16.47.255
Step 4 - Your subnet for Organisation with 4000 usable hosts is 198.16.32.0/20.
Network ID: 198.16.32.0
First usable host: 198.16.32.1
Last usable host: 198.16.47.254
Broadcast ID: 198.16.47.255
I have shown you the way for the first two. You can do the last two yourself as practice. Remember to first do the subnet with 4000 hosts and then the subnet with 2000 hosts. If you have any questions, don't hesitate to ask.