Given the network diagram.
Which address would successfully summarize only the networks seen?
A.
192.168.0.0/24
B.
192.168.8.0/20
C.
192.168.8.0/21
D.
192.168.12.0/20
E.
192.168.16.0/21
F.
These networks cannot be summarized.
Explanation:
let’s suppose it is a /20 then we would have addresses from 192.168.0.1 to 192.168.15.255
Now let’s suppose it is a /21 then we would have addresses from 192.168.8.1 to 192.168.15.255
So both summaries encompass the networks we want to summarize but the second one is the
most restrictive one as it only encompasses the networks we were asked to summarize and not
others so it is the correct summary.
In fact just count the number of subnets which is 8 and find the exponent of 2 which is 8, that gives
you 3 and to find out the summary mask just do /24 – 3 = /21.
if you make it in binary you’ll find out the answer too:
the interesting octet is 3rd one so let’s convert in binary.
8 0000 1000
9 0000 1001
10 0000 1010
11 0000 1011
12 0000 1100
13 0000 1101
14 0000 1110
15 0000 1111
I’ve bolded the bits in common there are 5 so 16+5=21 which is mask and address is 192.168.8.0