CIDR and Subnet Masks in Cloud Networking
You do networking on Cloud like #Azure and you tried to remember CIDR, subnet mask to determine available addresses with no success ?
Here is THE solution:
| Subnet Mask | CIDR | Binary Notation | Available Addresses Per Subnet |
|---|---|---|---|
| 255.255.255.255 | /32 | 11111111.11111111.11111111.11111111 | 1 |
| 255.255.255.254 | /31 | 11111111.11111111.11111111.11111110 | 2 |
| 255.255.255.252 | /30 | 11111111.11111111.11111111.11111100 | 4 |
| 255.255.255.248 | /29 | 11111111.11111111.11111111.11111000 | 8 |
| 255.255.255.240 | /28 | 11111111.11111111.11111111.11110000 | 16 |
| 255.255.255.224 | /27 | 11111111.11111111.11111111.11100000 | 32 |
| 255.255.255.192 | /26 | 11111111.11111111.11111111.11000000 | 64 |
| 255.255.255.128 | /25 | 11111111.11111111.11111111.10000000 | 128 |
| 255.255.255.0 | /24 | 11111111.11111111.11111111.00000000 | 256 |
| 255.255.254.0 | /23 | 11111111.11111111.11111110.00000000 | 512 |
| 255.255.252.0 | /22 | 11111111.11111111.11111100.00000000 | 1024 |
| 255.255.248.0 | /21 | 11111111.11111111.11111000.00000000 | 2048 |
| 255.255.240.0 | /20 | 11111111.11111111.11110000.00000000 | 4096 |
| 255.255.224.0 | /19 | 11111111.11111111.11100000.00000000 | 8192 |
| 255.255.192.0 | /18 | 11111111.11111111.11000000.00000000 | 16384 |
| 255.255.128.0 | /17 | 11111111.11111111.10000000.00000000 | 32768 |
| 255.255.0.0 | /16 | 11111111.11111111.00000000.00000000 | 65536 |
| 255.254.0.0 | /15 | 11111111.11111110.00000000.00000000 | 131072 |
| 255.252.0.0 | /14 | 11111111.11111100.00000000.00000000 | 262144 |
| 255.248.0.0 | /13 | 11111111.11111000.00000000.00000000 | 524288 |
| 255.240.0.0 | /12 | 11111111.11110000.00000000.00000000 | 1048576 |
| 255.224.0.0 | /11 | 11111111.11100000.00000000.00000000 | 2097152 |
| 255.192.0.0 | /10 | 11111111.11000000.00000000.00000000 | 4194304 |
| 255.128.0.0 | /09 | 11111111.10000000.00000000.00000000 | 8388608 |
| 255.0.0.0 | /08 | 11111111.00000000.00000000.00000000 | 16777216 |
| 254.0.0.0 | /07 | 11111110.00000000.00000000.00000000 | 33554432 |
| 252.0.0.0 | /06 | 11111100.00000000.00000000.00000000 | 67108864 |
| 248.0.0.0 | /05 | 11111000.00000000.00000000.00000000 | 134217728 |
| 240.0.0.0 | /04 | 11110000.00000000.00000000.00000000 | 268435456 |
| 224.0.0.0 | /03 | 11100000.00000000.00000000.00000000 | 536870912 |
| 192.0.0.0 | /02 | 11000000.00000000.00000000.00000000 | 1073741824 |
| 128.0.0.0 | /01 | 10000000.00000000.00000000.00000000 | 2147483648 |
| 0.0.0.0 | /00 | 00000000.00000000.00000000.00000000 | 4294967296 |
Why Understanding CIDR and Subnet Masks is Crucial ?
For Resource Allocation
CIDR and subnet masks play a pivotal role in resource allocation. An improper CIDR block can lead to inadequate or wasteful distribution of IP addresses.
For Security
Understanding these elements is also crucial for configuring firewalls and security groups, ensuring that only authorized traffic is allowed into your network.
For Cost Optimization
Using CIDR and subnet masks effectively can lead to cost optimization, particularly in cloud environments where IP address allocation may incur additional charges.
How to Use the Table ?
Quick Reference
The table serves as a quick reference to find the number of available addresses for a given CIDR block or subnet mask.
Planning Network Architecture
It can also be useful for planning your network architecture and deciding how to partition your IP address space.
Summary
Understanding CIDR and subnet masks is critical for anyone involved in network planning, security, and resource allocation, particularly in cloud environments like Azure. This table should serve as a comprehensive guide for quick identification of available IP addresses per subnet, thus aiding in effective network management and optimization.