5. Why Modern Media Networks Use /30 and /31 Networks

IP Address Strategies 

One of the defining characteristics of modern routed media networks is the widespread use of very small IP subnets. Engineers who have spent most of their careers working with traditional enterprise networks often expect to encounter large shared subnets such as:

• 192.168.1.0/24
• 10.10.10.0/24

Instead, they are often surprised to discover that modern ST 2110 facilities may contain hundreds or even thousands of individual point-to-point subnets, commonly implemented using:

• /30 prefixes
• /31 prefixes

At first glance, this can appear inefficient or unnecessarily complex. However, this approach is a deliberate design choice that provides significant operational and technical benefits. This chapter explains why small subnets are commonly used within Layer 3 media networks and how they contribute to the scalability and resilience of modern broadcast infrastructures.

The Traditional Layer 2 Approach

In conventional Layer 2 environments, it is common to place many devices within the same subnet. For example:

In this approach, all devices:

• Share the same broadcast domain
• Share the same subnet
• Communicate directly at Layer 2

This approach is simple and familiar. However, as discussed in previous chapters, larger Layer 2 domains can also increase:

• Failure domains
• Troubleshooting complexity
• Exposure to multicast-related events

Every Cable Becomes Its Own Network

One of the biggest conceptual changes when moving to a routed media network is that individual links are no longer viewed as part of a large shared network. Instead, each physical connection is treated as its own small IP network. In effect, every cable becomes its own routed segment, with a dedicated subnet assigned to the two devices connected by that link. Rather than sharing a subnet with dozens of other devices, each endpoint communicates across its own point-to-point network. Although this results in a much larger number of individual subnets, it also creates clear routing boundaries that improve fault isolation, simplify troubleshooting and make the overall network significantly more predictable.

Rather than thinking of the network as a collection of large shared LANs, it becomes a collection of small, individually routed links working together.

Routed Media Networks

Layer 3 media architectures adopt a fundamentally different philosophy. Rather than building large shared networks, they focus on creating many small, well-defined routing boundaries. A common approach is to treat each endpoint connection as an independent point-to-point relationship. For example:

Only two devices exist within this subnet:

• The endpoint
• The switch interface

The same pattern is repeated throughout the network. In a medium or large ST 2110 facility, this design may result in hundreds or even thousands of individual point-to-point subnets, each serving a single endpoint connection.

Instead of thinking:

the question becomes:

This represents a significant shift in design philosophy.

Why Not Use a /24?

A common question is why engineers do not simply place every endpoint within a large subnet such as a /24. After all, the devices would still be able to communicate, and significantly fewer subnets would be required. While this approach works in many traditional enterprise networks, it provides few advantages in a routed media environment. Every additional device placed within the same subnet increases the size of the broadcast domain and makes it less obvious which devices share the same Layer 2 network. By allocating a dedicated subnet to each point-to-point connection, every routed interface has a single, well-defined purpose. This improves operational clarity and makes the behaviour of the network much easier to predict.

Understanding /30 Networks

The most common subnet used for endpoint connections is the /30. Although small by enterprise networking standards, it provides exactly the number of addresses required for a dedicated point-to-point link. A /30 subnet provides four IP addresses:

This provides exactly two usable addresses. These are ideal for:

• Endpoint-to-switch connections
• Dedicated point-to-point relationships

Because each subnet serves a single purpose, clearly defined purpose, troubleshooting becomes significantly simpler.

Packet Walk

To understand why point-to-point subnets work so well, it is useful to follow a packet as it leaves an endpoint. Suppose Sender #1 (10.1.1.2/30) needs to send media to a receiver located elsewhere in the facility. The sender first determines that the destination does not exist within its own local subnet. Because the destination is remote, the sender forwards the packet to its configured default gateway, which is the switch interface at 10.1.1.1. The Layer 3 switch then performs a routing lookup, determines the best path towards the destination, and forwards the packet through the routed network until it reaches the subnet containing the receiver. At no point does the sender need to know anything about the rest of the network. Its only local relationship is with its directly connected gateway. Every other destination is reached through routing.

The Operational Benefits of /30 Networks

Smaller Failure Domains

If an issue occurs on a /30 subnet, its impact is naturally limited. Problems affecting one endpoint connection are isolated from neighbouring devices. Instead of affecting an entire VLAN, the issue is constrained to a single interface pair. This significantly reduces the network’s blast radius.

Improved Troubleshooting

When investigating an issue, engineers immediately know:

• Which endpoint is involved
• Which switch interface it connects to
• Which subnet should be inspected

There is no ambiguity regarding which devices share the network. This can substantially reduce the time required to identify faults.

Predictable Routing

Because every interface has a clearly defined purpose:

• Routing behaviour becomes more predictable
• Dynamic routing advertisements remain straightforward
• Network diagrams closely reflect operational reality

As facilities grow, this predictability becomes increasingly valuable.

Operational Consistency and Automation

Modern ST 2110 facilities may contain:

• Hundreds of cameras
• Processing nodes
• Multiviewers
• Gateways
• Monitoring systems

Applying the same addressing model consistently across every endpoint creates an infrastructure that is easier to understand, document and maintain. This consistency also makes automation significantly easier. Address allocation, documentation and configuration generation can all follow repeatable templates, reducing both deployment time and the likelihood of configuration errors. Collectively, these advantages explain why point-to-point subnetting has become standard practice in modern routed media networks. Although the addressing model initially appears unusual, it delivers a network that is easier to operate, easier to scale and significantly more resilient.

Address Efficiency Concerns

One of the most common questions is:

At first glance, this appears wasteful. However, private IPv4 address space provides almost 18 million addresses across the three RFC 1918 private address ranges. The operational benefits gained through improved fault isolation and predictability generally outweigh the relatively small increase in address consumption. For broadcast environments, engineers are often optimising for:

• Reliability
• Simplicity
• Maintainability

Rather than maximising address efficiency.

Introducing /31 Networks

While /30 networks are commonly used for endpoint connections, /31 networks may also be encountered. Unlike a /30 subnet, a /31 network contains only two addresses.

Modern networking standards allow both addresses to be used on point-to-point links. As a result, /31 networks are often used between network devices, such as:

• Leaf-to-Spine connections,
• Spine-to-Spine connections,
• Router interconnects.

Their use further reduces unnecessary address consumption while preserving the benefits of point-to-point design.

A Shift in Mindset

For many engineers, adopting /30 and /31 networks requires a change in perspective. Traditional network designs often begin by defining large subnets and placing devices within them. Routed media networks take the opposite approach. They begin by considering the relationship between interfaces. Instead of asking:

Engineers ask:

Once this mindset is adopted, the widespread use of small subnets becomes much easier to understand.

Preparing for Centralised Control

The use of small routed networks complements the principles discussed throughout this guide:

• Reduced failure domains
• Improved visibility
• Predictable behaviour
• Scalable growth

These characteristics form an important foundation for modern Layer 3 media networks. As facilities continue to evolve, some organisations choose to build upon these principles by introducing Software Defined Networking (SDN), enabling centralised awareness and control of increasingly large media environments.

In the next chapter, the guide explains how SDN-controlled media networks build upon these routed foundations by adding centralised awareness, automation and control.

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