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Is this right (subnetting)

Member Posts: 74 ■■□□□□□□□□
The following are notes I wrote down on sub-netting. Can someone take a look and let me know if I'm wrong in any points. Oh and what is the point of the "AND" math...it seems that I don't need to use it in my example...is it only for checking your work?

1. Look at Class (A,B,C )
2. Look at Mask (How many bits used in Host portion?)
3. Take “left-over” bits to determine range of hosts (minus zero and broadcast )

Example:
This is a class C network
Subnet Mask: 255.255.255.248 (aka 200.1.1.8 /29)
Network is using 5/8 of the host portion (remember, class C: N.N.N.H)
248 = 128+64+32+16+8 (5 out of the 8 bits, counted left to right)
Leftover bits is 3 (4+2+1) = range of seven including zero
200.1.1.8 “zero” host**
200.1.1.9
200.1.1.10
200.1.1.11
200.1.1.12
200.1.1.13
200.1.1.14
**Zero Address is simply when all the values to the right of the mask are 0’s, while the broadcast is when all the values to the right are 1’s. **

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Banned Posts: 12,312 ■■■■■■■■■□
Looks right. You use the AND operation when you have an IP address and a subnet mask, and you need to figure out which subnet that IP address belongs to. It's pretty obvious once you figure out the ranges, but that's how it works behind-the-scenes.
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Member Posts: 2,005
Yea that looks right for that network 200.1.1.8/29...one thing i always do like you did is find out the place where the last borrowed bit is. ie that last bit used in there is 8 so that will make the block size set to 8. So each subnet will interval by 8s, that just how I quickly can determine the network ranges in my head.
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Member Posts: 648
Looks good to me.

Helped me to pick it up quickly!
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Member Posts: 210 ■■■□□□□□□□
corretomundo
Think Big Stay Focus: In the midst of all situations, think positive.:thumbup:
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Member Posts: 154
Hi jrmeulemans

Just wondering what tools youo used to learn the technique? Ive been trying different methods still cant grasp it!

Thanks

Kev
LAB - 4 X 2651XM's 1 X 2620 3 X 2950 1 X 2509 AS 1 X 3550
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Member Posts: 201
In my opinion you cna't beat the Subnetting chapter in Todd Lammel's CCNA guide.
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Member Posts: 74 ■■□□□□□□□□
kevin31:

Cisco has a free e-learning section on their site that covers it:

http://www.cisco.com/E-Learning/bulk/subscribed/tac/cim/iprouting/basic_ip_routing_concepts/mod_frameset.htm

edit: oh yeah dude, you can also youtube a few decent vids on it....try and find one with an Australian guy with a whiteboard...