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Route Summarization (Cisco)

By emekusman ·
Hi everyone,
i seem to get stuck when I get to the subject of Route summarization. Look at this: summarizing through From the book it summarizes this to Using methods of summarization outlined (bits from the left which are common to all addresses) I got the summarized address as Could someone please explain this?

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by Joseph Moore In reply to Route Summarization (Cisc ...

I hate subnetting!
It really is the best place to learn this.

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by emekusman In reply to

Poster rated this answer.

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by mshavrov In reply to Route Summarization (Cisc ...

That's really easy:

Let's see what's common part between and To make it easier, will drop 172.16 part since it's noticable, and consider third octet:

16 = 0001 0000
31 = 0001 1111

So, first four bits stays the same and can be seen as "common" part.

First 2 octets (172.16) give us 16 bits of subnet mask, and we have extra 4 bits from the calculation above. Totally it's 20 bits, or sunetmask of

If you have more questions, e-mail me.

Good luck,

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by emekusman In reply to Route Summarization (Cisc ...

Got your response. What i want to really clarify is the summarized address of Why is it not

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