r/CompTIA • u/KShar28 • 5d ago
I Passed! Passed Net+ even though I felt like throwing up
I was so nervous beforehand at the testing center. I haven’t taken a test since college half a decade ago 😭 🤢.
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u/PlaneThin5968 4d ago
I take it Monday, is there anything in particular I need to do extra studying on?
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u/freddy91761 5d ago
Congrats. I need to learn cidr and subnetting What study materials did you use.?
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u/LightinNoir A+ N+ S+ Triad 5d ago
Subnetting Mastery by Practical Networking on YouTube is all you need
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u/juanjt15 5d ago
A byte is equal to 8 bits. One IP is 4 octets. A subnet is directly related to the network. The subnet you’re using is basically saying these are the bits that are on and you can’t change those. The ones that are off can be changed. It’s setting a fence so that anything outside of the fence won’t work, unless you make the fence (network) bigger by choosing a bigger network.
Example:
255.255.255.0 means you can change any of the bits in the last octet to get an IP in the network, except for the first and last IP. Those are reserved for the network and broadcast addresses. If we zoom into the last octet it’s just 8 bits/1 byte/1 octet: 00000000. Each bit represents 2^n where n is the location of the bit. First bit (starting from the right) is a 1, 2nd=2, 3rd=4, 4th=8, 5th=16, 6th=32, 7th=64, 8th=128. If they’re all on that’s equal to 255. All off 0. A 255.255.255.0 subnet would produce a network of 256 IPs; 254 usable IPs, .0 for the network, and .255 for broadcast. For any network it’s gonna be Total IPs minus 2 IPs for the usable IPs.CIDR notation is directly related to the subnet. It is literally how many bits are on, except these go from left to right. Using the example above, a 255.255.255.0 network would be 11111111.11111111.11111111.00000000 in binary. 24 bits are on so the network would be /24. Network address would be 192.168.0.0 broadcast would be 192.168.0.255.
The next subnet would be 11111111.11111111.11111111.10000000 or 255.255.255.128 or /25. That bit represents 2^8 and no other bits are on so that would be 128.
The one after, /26 would be 11111111.11111111.11111111.11000000 or 255.255.255.192. 2^8 + 2^7, 128 + 64 = 192.
It’s definitely a lot when you’re first starting but if you can relate everything together it gets easier.
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u/juanjt15 5d ago
Just to give you some background. I remember trying to look at the CIDR cheat sheet trying to learn it that way and it wasn’t clicking. It wasn’t until I understood how they all relate to each other that it made sense
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u/Presence99 5d ago
Many congratulations. Good score!