191 lines
3.0 KiB
Markdown
191 lines
3.0 KiB
Markdown
# Subnetting (Part 2)
|
||
|
||
## Problem
|
||
|
||
You have a network topology where each segment requires **45 hosts**:
|
||
|
||
```
|
||
45 hosts -> SW1 -> R1 <- SW3 <- 45 hosts
|
||
45 hosts -> SW2 -> R1 <- SW4 <- 45 hosts
|
||
```
|
||
|
||
You are given the network:
|
||
|
||
* **192.168.1.0/24**
|
||
|
||
Your task is to divide it into **4 subnets**, each capable of supporting at least 45 hosts.
|
||
|
||
---
|
||
|
||
## Step 1: Choose the Right Subnet Size
|
||
|
||
To support **45 hosts**, we need:
|
||
|
||
* ( 2^n - 2 \geq 45 )
|
||
* ( n = 6 ) → ( 2^6 - 2 = 62 ) hosts
|
||
|
||
So each subnet must be a **/26**.
|
||
|
||
---
|
||
|
||
## Step 2: Subnet Breakdown (/26)
|
||
|
||
Each subnet increases by **64 addresses**.
|
||
|
||
---
|
||
|
||
### Subnet 1
|
||
|
||
* **Network:** 192.168.1.0/26
|
||
* **Range:** 192.168.1.0 – 192.168.1.63
|
||
* **Broadcast:** 192.168.1.63
|
||
|
||
Binary:
|
||
|
||
```
|
||
11000000.10101000.00000001.00 000000
|
||
```
|
||
|
||
---
|
||
|
||
### Subnet 2
|
||
|
||
* **Network:** 192.168.1.64/26
|
||
* **Range:** 192.168.1.64 – 192.168.1.127
|
||
* **Broadcast:** 192.168.1.127
|
||
|
||
---
|
||
|
||
### Subnet 3
|
||
|
||
* **Network:** 192.168.1.128/26
|
||
* **Range:** 192.168.1.128 – 192.168.1.191
|
||
* **Broadcast:** 192.168.1.191
|
||
|
||
---
|
||
|
||
### Subnet 4
|
||
|
||
* **Network:** 192.168.1.192/26
|
||
* **Range:** 192.168.1.192 – 192.168.1.255
|
||
* **Broadcast:** 192.168.1.255
|
||
|
||
---
|
||
|
||
## Quick Trick 💡
|
||
|
||
Each subnet jumps by **64**:
|
||
|
||
* 0 → 64 → 128 → 192
|
||
|
||
Think of it like stepping stones across a river. Same stride, different landing spots.
|
||
|
||
---
|
||
|
||
## Subnetting Basics
|
||
|
||
* **Number of subnets:**
|
||
( 2^x ) (x = borrowed bits)
|
||
|
||
* **Number of hosts per subnet:**
|
||
( 2^n - 2 ) (n = host bits)
|
||
|
||
---
|
||
|
||
## Identify the Subnet
|
||
|
||
### Example 1
|
||
|
||
**Host:** 192.168.5.57/27
|
||
|
||
* /27 → block size = 32
|
||
* Subnets: 0, 32, 64, ...
|
||
|
||
57 falls between **32 and 63**
|
||
|
||
→ **Network:** 192.168.5.32/27
|
||
|
||
---
|
||
|
||
### Example 2
|
||
|
||
**Host:** 192.168.29.219/29
|
||
|
||
* /29 → block size = 8
|
||
* Subnets: 0, 8, 16, ..., 216, 224
|
||
|
||
219 falls between **216 and 223**
|
||
|
||
→ **Network:** 192.168.29.216/29
|
||
|
||
---
|
||
|
||
## Class C Reference Table
|
||
|
||
| Prefix | Subnets | Hosts |
|
||
| ------ | ------- | ----- |
|
||
| /25 | 2 | 126 |
|
||
| /26 | 4 | 62 |
|
||
| /27 | 8 | 30 |
|
||
| /28 | 16 | 14 |
|
||
| /29 | 32 | 6 |
|
||
| /30 | 64 | 2 |
|
||
|
||
---
|
||
|
||
## Subnetting Class B Networks
|
||
|
||
The method is exactly the same. Only the starting mask changes.
|
||
|
||
---
|
||
|
||
### Example 1
|
||
|
||
**Network:** 172.16.0.0/16
|
||
**Required subnets:** 80
|
||
|
||
* ( 2^7 = 128 ) → enough
|
||
* New prefix: **/23**
|
||
|
||
---
|
||
|
||
### Example 2
|
||
|
||
**Network:** 172.22.0.0/16
|
||
**Required subnets:** 500
|
||
|
||
* ( 2^9 = 512 )
|
||
* New prefix: **/25**
|
||
|
||
---
|
||
|
||
### Example 3
|
||
|
||
**Network:** 172.18.0.0/16
|
||
**Required subnets:** 250
|
||
|
||
* ( 2^8 = 256 )
|
||
* New prefix: **/24**
|
||
|
||
---
|
||
|
||
## Class B Reference Table
|
||
|
||
| Prefix | Subnets | Hosts |
|
||
| ------ | ------- | ----- |
|
||
| /17 | 2 | 32766 |
|
||
| /18 | 4 | 16382 |
|
||
| /19 | 8 | 8190 |
|
||
| /20 | 16 | 4094 |
|
||
| /21 | 32 | 2046 |
|
||
| /22 | 64 | 1022 |
|
||
| /23 | 128 | 510 |
|
||
| /24 | 256 | 254 |
|
||
|
||
---
|
||
|
||
## Final Review
|
||
|
||
* Subnetting is about **borrowing bits**
|
||
* Larger prefix = more subnets, fewer hosts
|
||
* Smaller prefix = fewer subnets, more hosts |