Hub & Spoke, what is the recommended hub size?

Question

In designing a virtual network (VNet) for a hub in a hub & spoke model, what is the recommended size for the hub? Should it be a /20, /22, or /23?

Any advice or best practices would be appreciated, especially since the official Microsoft documentation does not clarify this aspect.

thank you

Answer 1

@ares

Greetings!

The size of the hub VNet in a hub-and-spoke model depends on your current and future requirements, such as the number of subnets, connected spokes, and services hosted in the hub.

A larger address space (e.g., /20) provides more flexibility for adding subnets in the future.

For smaller setups with limited growth, a /22 or /23 might suffice, but it could limit future expansion.

/20 Subnet: This is often the recommended size for the hub VNet. A /20 subnet provides 4,096 IP addresses,This allows for significant growth and the addition of various services, such as virtual appliances, gateways, and other resources.

/22 Subnet: This provides 1,024 IP addresses, which may be sufficient for smaller deployments but could become limiting as your architecture grows.

/23 Subnet: This offers only 512 IP addresses, which is generally too small for a hub VNet, especially in a hub-and-spoke architecture where you may need to accommodate multiple services and connections.

For more about Hub-spoke network topology in Azure

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