Be better at subnetting and routing

In traditional subnetting, you divide a network into equal-sized subnets using a fixed subnet mask. For example, if you have a Class C network (e.g.,, you can divide it into multiple subnets, each with 256 (2^8) addresses.

By mastering IP subnetting techniques like VLSM, Supernetting, CIDR, and summarization you can use IP addresses with precision and elegance.


VLSM stands for Variable Length Subnet Masking. It’s a technique used in IP network design to allocate IP addresses efficiently and reduce waste.

With VLSM, you can divide an IP network into smaller subnets of different sizes, each with its own subnet mask.

VLSM is particularly valuable in scenarios where you have various network segments with different requirements, such as different departments in a company or different customer networks in a service provider’s environment. It helps conserve IP address space and optimizes network utilization.

Imagine you have a Class C network, say, and you want to divide it into smaller networks for different purposes. VLSM is your tool of choice.

  • Subnet 1 (Sales): You might need 30 addresses here. Use a /27 mask to get 32 addresses, leaving 2 unused.
  • Subnet 2 (Marketing): They need 12 addresses. A /28 mask gives you 16, leaving 4 idle.
  • Subnet 3 (IT): IT requires 6 addresses. Use a /29 mask for 8 addresses, with 2 free.

VLSM lets you fine-tune your subnets, making sure no IP goes to waste.


CIDR, or Classless Inter-Domain Routing, is a notation used to efficiently represent and manage IP address ranges and subnet masks by specifying the base address followed by a forward slash and the subnet mask length (e.g., It simplifies IP address allocation and routing.


Instead of dividing, you group multiple smaller networks into a bigger one, simplifying routing.

  • Subnet 1:
  • Subnet 2:

Combine them into a supernet: This is a bigger network, covering both subnets. It’s routing efficiency at its best!


Summarization, also known as route aggregation, is about combining multiple subnets into a single, larger one.

  • Subnet 1 (Sales): /27
  • Subnet 2 (Marketing): /28
  • Subnet 3 (IT): /29

Summarize them as This simplifies routing tables and keeps things tidy.

Supernetting and summarization are related concepts in networking, but they serve slightly different purposes.

In summary, the key difference is that supernetting typically involves combining contiguous subnets to simplify routing within a single network, while summarization (route aggregation) encompasses combining routes from multiple networks, often at network boundaries, to simplify routing between networks. Both techniques aim to optimize routing tables and reduce the size of routing updates, but they operate at different scales and in different contexts.