Subnet mask question

StarPuppy SG

i am not too sure about the answer..can u guys help? Confused

Question: If you have been given this IP ad - 192.108.100.0, what network mask should you use if you want EIGHT separate broadcast domains

Answer:

2(4) = 16
256-16 = 240
Subnet Mask = 255.255.255.240

manyu882 SG

the calculater says 255.255.255.224

http://www.subnet-calculator.com/subnet.php?net_class=C

StarPuppy SG

yes..however it is assumed that it require all of the 8 subnets are usable

ndmmxiaomayi SG

But that’s not true in real life. In real life, the first and the last subnet is not usable.

StarPuppy SG

EIGHT separate broadcast domains

does it mean that all 8 are working?

ndmmxiaomayi SG

All 0s = calculate subnet address
All 1s = calculate broadcast address

How many do you think you have if you use 2^3?

StarPuppy SG

8 but only 6 are usable

but is the question stating it wants 8 usable?

ndmmxiaomayi SG

You ask me, I ask who?

You asked this question, isn't it? Laughing

StarPuppy SG

i blur ma..dun understand the question

Laughing

ndmmxiaomayi SG

Deleted.

Found out why liao.

http://www.ralphb.net/IPSubnet/example.html

Mr. Green

manyu882 SG

hmm i'm starting to get this.. do u mean u want 8 valid IP addresses?
according to the calculator..
u only can have (these are class c)
1 sub nets each 254hosts
(notice the 2 ends of ip address.. the more subnet, the more hosts wasted)
2 subnets 126 vaild hosts
4 subnets 62 vaild hosts
8 subnets 30 vaild hosts
16subnet 14 vaild hosts
32 subnet 6 vaild hosts

if u want to make 8 its impossible... correct me if wrong. either u get 6 or 14

ndmmxiaomayi SG

Borrow bits...

6 is not enough.

14 is more than enough, so 14 is used.

StarPuppy SG

naturally..but if its asking for 8 valid subnets..the closest would be 14