Subnetting

marcj04

Hey guys,
I've been studying for the Network+ and I was just wondering how important is Subnetting in the real world? Do network admins and engineers find them Subnetting quite often? I find it fun and I want to get really good at it but if it's not even that much of a used skill, then I guess I won't bother. It does seem really useful to me but then again I've never actually worked in a networking environment yet.

d4nz1g

Every single day.
I guess it is the most important thing you need to know

joelsfood

VERY useful. To be fair, a lot of engineers/designs just try to use a single /24 per Vlan, etc, but even there, you'll ha ve to break it out as soon as you get a hiring spike, etc. So definitely learn it, don't just cram in the minimum required for the test.

10Linefigure

We use it often, especially in the lab. Learn it and you will be better off at work and later when you study for harder exams.

kohr-ah

Always useful. This is how I always remember it below to see ranges at least:

What is the range per group? Subtract subnet mask from 256.
ex: 255.255.255.240 so subtract 240 from 256 and it tells you the subnets go in 16s. 192.168.0.0, 192.168.0.16, 192.168.0.32, etc.
255.255.224.0 so subtract 224 from 256 and it tells you subnets go in 32s. 10.0.0.0, 10.0.32.0, 10.0.64.0, 10.0.96.0, etc.

Wild cards for ACLs subtract from 255.
ex: 255.255.255.248 so subtract 248 from 255 and it tells you the ACL would be 0.0.0.7
255.255.192.0 so subtract 192 from 255 and it would be 0.0.63.255

Kragster

Agree with the others, but will mention that in your environment you'll find yourself using the same masks over and over so you won't even have to do the math anymore eventually. Once you've done it enough it will be just automatic.

Keep doing the practice stuff and find a method that works for you when you have to do the math on the lesser used subnets. Eventually it will all click and you won't have to do math on the common masks/cidr notations anymore, you'll just know the answer as soon as you see the setup.

fuz1on

Net Mask | # of hosts | Bits | Network | Host

255.255.255.0 | 255^(2^ hosts | 24 | 192.168.5 | 3

255.255.0.0 | 255*255^(2^16) hosts | 16 | 192.168 | 5.3

255.0.0.0 | 255*255*255^(2^24) hosts | 8 | 192 | 168.5.3

*Increasing hosts, decreasing networks*

Copied this down into my notes from somewhere on the web.

kohr-ah - tight!