Route Summarization

computer g33k

I'm working on my study guide and I'm confused by this question. The question is "you have been addressed a group of networks by subnetting 192.168.1.0/24. How could you best summarize the following subnets?

192.168.1.128/27
192.168.1.160/27
192.168.1.192/27
192.168.1.224/27

I'm not sure if I got right answer or not. I got 192.168.1.0 Subnet Mask 255.255.255.224

Todd Burrell

Since the addresses go from 192.168.1.128 to 192.168.1.255 I would have answered the summarization as follows:

Network 192.168.1.128
Mask 255.255.255.128

This completely covers all 4 subnets you listed below with no waste...

I'm still a little unsure about some summary routes, but they MUST completely cover ALL of the addresses in ALL of your subnets. That I do know. So looking at the 4 subnets you have, the first address of the first subnet is 192.168.1.128 and the broadcast address of the last subnet is 192.168.1.255.

martell1000

This is correct putting summarizing to two /27s always gives you a /26 mask and summarizing 2 /26s gives you /25 which covers all 128 addresses.

fsanyee

check the network addresses:
192.168.1.10000000
192.168.1.10100000
192.168.1.11000000
192.168.1.11100000
look for the last bit, where all the adresses are match and you got the summarized network addr:
192.168.1.128 with mask 255.255.255.128
(i wrote only the last byte in binary, because there is no change in the first three.)