What Do We Know?
Written on 11:28 by Ahmet Emir
Okay—here’s area you can absolutely administer what you’ve abstruse so far, and activate committing
it all to memory. This is a actual air-conditioned area that I’ve been application in my classes for years. It will
really advice you attach bottomward subnetting!
When you see a subnet affectation or carve characters (CIDR), you should apperceive the following:
/25 What do we apperceive about a /25?
- 128 mask
- 1 $.25 on and 7 $.25 off (10000000)
- Block admeasurement of 128
- 2 subnets, anniversary with 126 hosts
/26 What do we apperceive about a /26
- 192 mask
- 2 $.25 on and 6 $.25 off (11000000)
- Block admeasurement of 64
- 4 subnets, anniversary with 62 hosts
- 224 mask
- 3 $.25 on and 5 $.25 off (11100000)
- Block admeasurement of 32
- 8 subnets, anniversary with 30 hosts
/27 What do we apperceive about a /27?
/28 What do we apperceive about a /28
- 240 mask
- 4 $.25 on and 4 $.25 off
- Block admeasurement of 16
- 16 subnets, anniversary with 14 hosts
- 248 mask
- 5 $.25 on and 3 $.25 off
- Block admeasurement of 8
- 32 subnets, anniversary with 6 hosts
/29 What do we apperceive about a /29?
/30 What do we apperceive about a /30?
- 252 mask
- 6 $.25 on and 2 $.25 off
- Block admeasurement of 4
- 64 subnets, anniversary with 2 hosts
Regardless of whether you accept a Class A, Class B, or Class C address, the /30 affectation will
provide you with alone two hosts, ever. This affectation is ill-fitted about exclusively—as able-bodied as suggested
by Cisco—for use on point-to-point links.
If you can acquire this “What Do We Know?” section, you’ll be abundant bigger off in your
day-to-day job and in your studies. Try adage it out loud, which helps you acquire things—
yes, your cogent added and/or coworkers will anticipate you’ve absent it, but they probably
already do if you are in the networking field. And if you’re not yet in the networking acreage but
are belief all this to breach into it, you ability as able-bodied accept bodies alpha cerebration you’re an odd
bird now back they will eventually anyway.
Subnetting Basics 127
It’s additionally accessible to address these on some blazon of flashcards and accept bodies analysis your skill.
You’d be afraid at how fast you can get subnetting bottomward if you acquire block sizes as well
as this “What Do We Know?” section.
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