Subnet question

[cisco222]

the network 172.25.0.0 has been devided into 8 equal subnets. Which of the following ip addresses can be assigned to in the third subnet if the ip- subnet zero is configured on the router?

Possible Answers
A= 172.25.78.243
B=172.98.16
C=172.25.72.0
D=172.25.94.255
E=172.25.96.17
F=172.25.100.16

anwser is A C and D however i'm not 100% sure how to this anwser.

I worked out the following

128 64 32 16 8 4 2 1
1 0 0 0 takes 4 bit's to get 8

128 64 32 16 8 4 2 1 our loweest number is 16 so we increment by this? when looking how this anwser was worked out i can see people
1 1 1 1 incrementing by 32 how and why do they use 32?

Thanks

 

[perchanski]

Hi

It takes 3 bits to get to 8 (2 to the power of 3 = 8)
Then you use 128 64 32 16 8 4 2 1
1 1 1 0 0 0 0 0

Which is the 32 range for 8 equal subnets

 

[imbadatthis]

or yo know :
256/8 = 32
start counting
0 ... 31
32 ... 63
64 ...95 <--- answer third subnet.
172.25.64.0 - 172.25.95.255



We must go always forward, not backward
always up, not down and always twirling twirling towards infinity.