Need help understanding IP question?

rphann

Can someone help me understand why the answer is "B". Thanks.

You work as the network administrator at Contoso.com. The Contoso.com network consists of a single Active Directory domain named contoso.com. The Contoso.com network contains a Dynamic Domain Name System (DDNS) server named Server01 and a File Server named Server02. Server01 uses the IP address 192.168.2.143/27 and Server02 uses the IP address 192.168.2.145/27.

You Windows XP Professional client computer is named Client01. Client01 is configured with the IP address 192.168.2.159/27 and a gateway address of 192.168.2.129/27. You are unable to connect to Server02. You need to access files on Server02.

What should you do?
a. Change the IP address on Server01 to 192.168.2.165
b. Change the IP address on Client01 to 192.168.2.158 (Correct Answer)
c. Change the IP address on Server02 to 192.168.2.129
d. Change the gateway address on Client01 to 192.168.2.163

dynamik

192.168.2.159 would be the broadcast address for that subnet.

It always helps to write things out in binary:
11000000.10101000.00000010.10011111

Remember, you can't use all 0s (network address) or all 1s (broadcast address) for a host. That's why you have to subtract two when determining the max number of hosts on a subnet.

rphann

Thanks for the reply, but I still don’t understand why we have to change the IP address for Client01 from 192.168.2.159 to 192.168.2.158. If the subnet mask is /27, shouldn’t they all be able to communicate?

11111111.11111111.11111111.11100000 = /27
11000000.10101000.00000010.10011111 = 192.168.2.159 (client01)
11000000.10101000.00000010.10001111 = 192.168.2.143 (server01)
11000000.10101000.00000010.10010001 = 192.168.2.145 (server02)
11000000.10101000.00000010.10010001 = 192.168.2.129 (default gateway)

11000000.10101000.00000010.10011110 = 192.168.2.158

dynamik

See the note at the bottom of my previous post. All the host bits are set to 1, which is the broadcast address for that subnet. The broadcast and network addresses are reserved for their respective purposes. Therefore, you can't set a host's IP to the broadcast address.

http://en.wikipedia.org/wiki/Broadcast_address

rphann

Thanks dynamik! I appreciate your help.