General discussion

Locked

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 172.16.16.0 through 172.16.31.0. From the book it summarizes this to 172.16.0.0/20. Using methods of summarization outlined (bits from the left which are common to all addresses) I got the summarized address as 172.16.16.0/20. Could someone please explain this?

This conversation is currently closed to new comments.

4 total posts (Page 1 of 1)  
| Thread display: Collapse - | Expand +

All Comments

Collapse -

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

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

Collapse -

by emekusman In reply to

Poster rated this answer.

Collapse -

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

That's really easy:

Let's see what's common part between 172.16.16.0 and 172.16.31.0. 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 255.255.240.0.

If you have more questions, e-mail me.

Good luck,

Collapse -

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

Got your response. What i want to really clarify is the summarized address of 172.16.0.0/20. Why is it not 172.16.16.0/20?

Back to Networks Forum
4 total posts (Page 1 of 1)  

Related Discussions

Related Forums