I dont understand the answer to this question

newtechie1988

I am trying to learn and route summarization but I dont understand how to do questions like these. could somebody please help me? (* indicates answer)
A router has a summary route to network 192.168.32.0/20 installed in its routing table. What range of networks are summarized by this route?
192.168.0.0 – 192.168.32.0/24
192.168.0.0 – 192.168.47.0/24
*192.168.32.0 – 192.168.47.0/24
192.168.32.0 – 192.168.48.0/24
192.168.32.0 – 192.168.63.0/24

mella060

Firstly, how is your subnetting ? You really need to have that down pat before you dive into route summarization.

First thing i would look to find is the increment / block size. Write down the address...192.168.32.0 /20 or 255.255.240.0

To find your increment, subtract 240 from 256....256-240 = 16...or they way i like to do it is to find the last bit position where the value is a 1.

Write out your subnet mask in binary.

/20 = 11111111.11111111.11110000.00000000

128 64 32 16 8 4 2 1

Get the idea ?

Ok so the increment is 16 in the 3rd octet. Your networks and their range of addresses would be as follows...

192.168.0.0 - 192.168.0.1 - 192.168.15.254
192.168.16.0 - 192.168.16.1 - 192.168.31.254
192.168.32.0 - 192.168.32.1 - 192.168.47.254
192.168.48.0 - 192.168.48.1 - 192.168.63.254
192.168.64.0 - 192.168.64.1 - 192.168.79.254