====== subnetting cheatsheet======
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===== context=====
dit document beschrijft hoe subnetting in mekaar zit

===== 1. IP Address Structure =====
IPv4 addresses are **32-bit** numbers divided into 4 octets:

<code>
192.168.10.5
| 8 bits | 8 bits | 8 bits | 8 bits |
</code>
===== 2. Classes (Old Way, Still Useful) =====
^ Class ^ First Octet Range ^ Default Mask ^ Use ^
| A | 1–126 | /8 | Large networks |
| B | 128–191 | /16 | Medium networks |
| C | 192–223 | /24 | Small networks |
| D | 224–239 | N/A | Multicast |
| E | 240–254 | N/A | Experimental |

----

===== 3. Subnet Mask Basics =====
A subnet mask tells which part is **network** and which part is **host**.

Example:

<code>
255.255.255.0  → /24
</code>

----

===== 4. CIDR Notation =====
^ Subnet Mask ^ CIDR ^
| 255.0.0.0 | /8 |
| 255.255.0.0 | /16 |
| 255.255.255.0 | /24 |
| 255.255.255.128 | /25 |
| 255.255.255.192 | /26 |
| 255.255.255.224 | /27 |
| 255.255.255.240 | /28 |
| 255.255.255.248 | /29 |
| 255.255.255.252 | /30 |

----

===== 5. Subnetting Steps (Fast Method) =====

==== Step 1: Convert mask to binary ====
Example:

<code>
/26 = 255.255.255.192
= 11111111.11111111.11111111.11000000
</code>

==== Step 2: Find number of subnet bits ====
* /26 has **2 bits** for subnet (since default /24 + 2)

==== Step 3: Calculate number of subnets ====
<code>
2^subnet_bits
= 2^2 = 4 subnets
</code>

==== Step 4: Calculate hosts per subnet ====
<code>
2^(host_bits) - 2
= 2^6 - 2 = 62 hosts
</code>

----

===== 6. Shortcut: Subnet Increments =====
If you know the subnet mask, the increment is the value of the **last 1 bit** in the mask.

Example:  
**/26 mask = 255.255.255.192**

<code>
Binary: 11000000
Increment = 64
</code>

So subnets:

<code>
0, 64, 128, 192
</code>

----

===== 7. Key Rules =====
* **Network address**: all host bits = 0  
* **Broadcast address**: all host bits = 1  
* **Cannot use network or broadcast addresses for hosts**

----

===== 8. Common Subnetting Values =====
^ Mask ^ Subnet Size ^ Hosts ^
| /24 | 256 | 254 |
| /25 | 128 | 126 |
| /26 | 64 | 62 |
| /27 | 32 | 30 |
| /28 | 16 | 14 |
| /29 | 8 | 6 |
| /30 | 4 | 2 |

----

===== 9. Practice Example =====
**Given:** 192.168.1.0 /26  
**Find subnets and ranges**

Subnets (increment 64):

<code>
192.168.1.0   → hosts .1 to .62  → broadcast .63
192.168.1.64  → hosts .65 to .126 → broadcast .127
192.168.1.128 → hosts .129 to .190 → broadcast .191
192.168.1.192 → hosts .193 to .254 → broadcast .255
</code>

----

===== 10. Useful Mnemonic =====
**“Network, Subnet, Host”**  
Think of it as:

* Network = **fixed**
* Subnet = **variable**
* Host = **variable**
===== meer info =====
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