3.3.i Implement optimize and troubleshoot manual and auto summarization with any routing protocol

a guy at work asked me yesterday about summarization… he’s planning to take the ccna in a couple of months… the first thing i asked him was, did he understand subnetting and classful boundaries… the next thing i asked him was, did he understand powers of 2… i determined he was on the money so i told him the way i figure it out…

first, you must understand how to determine summarization with binary… why? because you must crawl before you run…

then, summarization can be determined with powers of 2 easily…

the initial supposition is that the aggregated route will be less than the classful boundary it rests on..

for example,if you have 172.16.1.1, 172.16.2.1 and 172.16.3.1/24 and you want to summarize, look at the third octet… the numbers 1 2 and 3 are the range…

the numbers 1 2 and three fall within the range of 4… 2 to the second = 4… in other words it takes 2 twos to get to four, or to encompass the range… subtract 2 from /24 and you have /22… or in binary count the bits up to where they change, as below…

10101100 00010000 00000001 00000001
10101100 00010000 00000010 00000001
10101100 00010000 00000011 00000001

if the range of numbers is 8: 2 to the third gets to 8… subtract 3 from /24 and you have /21…

it’s that easy if you’ve done the prior heavy lifting…