Side view of black laptop keyboardWhen creating an enterprise campus network design, the two most common models used are the three-tier and two-tier layered models. The two-tier model is often considered the best option for small or medium campus networks and is commonly referred to as collapsed core architecture. Understanding the differences in this model and how they impact your network is necessary to determine whether this is the right option for your enterprise.

What Is Collapsed Core Architecture?

In the standard three-tier model, the campus network consists of three layers made up of functional distribution layer blocks. The core layer handles transport between sites and provides for routing needs. It handles server and internet connections. Network failures at this level can have a significant impact, so it’s crucial this layer be designed with resilience in mind so it can recover quickly. The access layer provides network access to end users. This includes connections to devices, such as PCs and tablets. The distribution layer manages connectivity between the core and access layers, based on policies and boundaries worked into the network. In collapsed core architecture, the core and distribution layers are combined, simplifying the design.

The three-tier model is necessary for complex campuses that require access by multiple sites, devices and users. It results in a network that is scalable, cost-efficient and reliable for large enterprises. However, smaller campuses can reap similar benefits with a simpler model, scaled down to improve costs and oversight.

Benefits of Collapsed Core Networks

Collapsed core networks largely function in the same way as their larger, three-tiered counterparts. However, there are some benefits unique to the collapsed core model that make it a better option for smaller campuses.

Lower Costs

Collapsed core networks can save the company money by reducing the amount of hardware needed to build and run the network. By combining the core and distribution layers, this model eliminates the need for separate devices. This offers companies the chance to utilize most of the benefits offered by the three-tiered model in a budget-friendly option.

Simplified Network Protocols

The protocols needed to run a collapsed core network are less complex. With only two layers requiring communication, there are fewer opportunities for network protocol issues.

Designed for Small Campuses

Because the collapsed core model was derived from the three-tiered model, the model was designed to cater to small and medium campus needs. This ensures these campuses can utilize the relevant benefits of the three-tiered model without the need to worry about unnecessary equipment or oversight.

Limitations of Collapsed Core Networks

Although the collapsed core network models are designed to offer smaller business campuses access to the three-tier model’s benefits, there are some limitations created in the trade-off.


The scalability of collapsed core networks is limited, making it difficult for rapidly growing campuses to adjust for additional sites, devices and users. According to Cisco, a small network provides access to up to 200 devices, while a medium network provides access to up to 1000. This means the collapsed core model was designed to handle this level of access without regard to anything beyond. Campuses that anticipate this kind of growth may need to consider switching to three layers to handle the excess. Fortunately, the transition is relatively simple when necessary.


The collapsed core design also loses some of the resiliency found in the three-tier model. With fewer devices needed to run the network, there is a lower redundancy to cover the failures of individual components. This doesn’t mean the network isn’t reliable, but there is some loss associated with the scaled-down nature of the collapsed core design.


Manageability is impacted for the same reason. A lack of redundancy can make it more difficult when a faulty component needs to be replaced or a distribution policy needs to be adjusted. If network downtime is anticipated, this will need to be considered before scheduling changes.

Should I Choose a Collapsed Core Design?

For small and medium campuses that want the power of a three-tiered network but lack the budget and technical know-how to maintain it, a collapsed core network can provide a similar experience for less. Although there are some limitations to consider for campuses that anticipate rapid growth, the switch to the full three-tiered design is simple enough, leaving very little doubt that a collapsed core network is the best solution for smaller enterprises. Need any IT network support to help with the maintenance of your collapsed core network? Contact EIRE Systems today.

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About the Author: EIRE Systems

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EIRE Systems is a leading independent provider of professional IT, AV and Access Security services to the financial, insurance, manufacturing, health care, retail, construction, hospitality, commercial real estate, legal, educational and multinational sectors in Japan and throughout the Asia Pacific region. EIRE Systems has expertise across a wide spectrum of Information Technologies, with a track record for successfully completing hundreds of assignments since its establishment in 1996.