Planning – IP Subnets

Creating a scalable and effective IP address scheme is crucial for network administration. This ensures the network is organized, scalable, and prevents IP address conflicts. You can still manage your IP scheme without IP Address Management (IPAM) software by using a simple Excel spreadsheet, though keep in mind it may be more labor-intensive and error-prone than using specialized software.

Here is a step-by-step guide on how to design your IP subnetting scheme:

Step 1: Determine the Scope of Your Network

Consider the current number of devices and how many devices you expect to have in the future. This will help you determine the size of your IP address pool.

If you’re using a private IPv4 addressing scheme, your available address ranges are: – – –

IPv6 offers a much larger address space if you decide to go in that direction.

Step 2: Consider Network Segmentation

Do you need to separate different types of devices or different business units into separate subnets? If so, you should plan your addressing to accommodate this.

For example, you might use 10.0.x.x/24 for your servers, 10.1.x.x/24 for your desktops, 10.2.x.x/24 for your IoT devices, and so forth.

Step 3: Plan for Future Growth

Subnetting involves splitting an IP network into smaller networks. To plan for future growth, avoid creating subnets that fit your needs exactly today. Instead, consider creating larger subnets that provide room for expansion.

A common practice is to use /24 subnets (providing up to 254 usable addresses), which are usually more than sufficient for most subnets while remaining small enough to limit the size of broadcast domains.

Step 4: Document Your IP Scheme

Now you can create your IP scheme in Excel. Create a sheet for each subnet and include the following details for each IP address:

  • IP Address
  • Subnet Mask
  • Default Gateway
  • Device Name
  • Device Type
  • MAC Address
  • Location
  • Any other notes

You can also create an overview sheet that shows which IP address ranges have been assigned to which subnets. This will help you quickly see which ranges are still available for future use.

Step 5: Keep It Updated

Ensure that your IP scheme is kept up-to-date. An outdated scheme can lead to misconfigurations and IP address conflicts. This task can be tedious, especially for larger networks, but it is crucial.

In the long run, consider investing in IPAM software. Not only does it make managing your IP scheme easier, but it also offers additional benefits like discovery and tracking, DNS and DHCP integration, and reporting.

Remember, creating a solid IP addressing scheme from the beginning is much easier than trying to organize a disorganized IP environment later on. Always keep the future in mind when planning out your IP addresses and subnets.


Planning is a key factor in many areas of technology and business, and network design, including IP subnetting, is no exception. While not the only important aspect, it forms the basis of effective network management and growth. Here are a few reasons why planning is essential:

  1. Scalability: Proper planning ensures your network is ready to grow with your organization. Without it, you may find your network resources stretched thin as your business expands, leading to potential downtime and costly reconfiguration efforts.
  2. Efficiency: A well-planned network ensures that resources are used efficiently. This includes IP addresses, network hardware, and even network administrators’ time.
  3. Performance: Good planning helps prevent performance issues caused by overcrowded subnets and inefficient routing. By distributing your network load across multiple subnets, you can help ensure smooth network operation.
  4. Security: Planning your network layout can improve security by isolating different types of traffic. For example, you could keep sensitive data on a separate subnet from general traffic to reduce the risk of a data breach.
  5. Troubleshooting: If issues do arise, a well-documented and well-planned network makes it easier to diagnose and resolve problems.

While planning is crucial, it’s also important to be flexible and ready to adjust your plans as needed. Technology and business needs can change rapidly, and what worked well when you first designed your network might not be the best approach a year or two down the line.

As such, remember to regularly review and update your network plan as part of your ongoing network administration duties. It’s not a one-and-done task but rather an ongoing process.


When designing an IP address scheme for an enterprise, it’s essential to keep in mind network growth, network segmentation, and ease of troubleshooting. Here’s a simplified example of an IP address scheme using a private IPv4 address space:

  1. Global Servers and Services ( This range can be used for services that are accessed throughout the organization, such as DNS servers, email servers, or application servers. Subnets within this range might be further broken down based on function, for instance:
  • DNS Servers:
  • Mail Servers:
  • Application Servers:
  1. Local Offices / Departments ( – Assign each office or department a different /16 range. This allows each office to have multiple /24 subnets for different types of devices, and also simplifies routing between offices. For example:
  • Head Office:
  • Branch Office A:
  • Branch Office B:

Each office can then have its subnets, for instance, within the Head Office range:

  • Desktops:
  • Printers:
  • Wi-Fi Devices:
  1. Data Centers ( – Assign each data center a /16 range as well, subdividing it into /24 subnets based on the type of servers.
  2. VPN Users ( This range could be used for remote users connecting to the company network over a VPN.
  3. Reserved for future use ( – Keep the rest of the address space for future growth.

Remember, this is just an example and your IP address scheme should be tailored to your organization’s specific needs. A similar scheme can be used for IPv6 addressing as well, although IPv6 provides a significantly larger address space.

This plan should also be documented and kept updated as changes are made. By doing so, you create an easily understood network map that will be a vital resource for network troubleshooting and future planning.

One thing I like to do is to use the third octet, use either a 1 or 2 when choosing subnet blocks for routing. Path A would use 1 and Path B would use 2. This way when I’m doing traceroutes, I can see which PATH it’s using and it points out if there was a failover somewhere.

10.10.1.x = PATH A
10.10.2.x = PATH B

10.20.1.x = PATH A
10.20.2.x = PATH B

Branch 1:
10.101.1.x = PATH A
10.101.2.x = PATH B

Branch 2:
10.102.1.x = PATH A
10.102.2.x = PATH B