Visual Subnet Calculator (Azure Edition)
Enter the network you wish to subnet:
Click below to split and join subnets.
Tips for Azure Virtual Network
Azure Reserved Subnet Name
|Reserved Subnet Name||min. Size of Subnet||Max. Size of Subnet||Recommand Size of Subnet||Related Azure Services|
|GatewaySubnet||/29||/26||/27||Azure Virtual Network Gateway / ExpressRoute / Site-to-Site VPN|
|RouteServerSubnet||/27||/24||/27||Azure Route Server|
|AzureFirewallManagementSubnet||/29||/26||/29||Azure Firewall Manager|
Common Subnet Size
|Common Subnet Name||min. Size of Subnet||Max. Size of Subnet||Recommand Size of Subnet||Related Azure Services|
|snet-in-dns-resolver||/28||/24||/28||Azure Private DNS Resolver|
|snet-out-dns-resolver||/28||/24||/28||Azure Private DNS Resolver|
Sample CIDR Plan
If you only have one /24 that can be designed...
Based on Are there any restrictions on using IP addresses within these subnets?, Azure Subnet reserves 5 IP addresses in each subnet for internal use: the first 4 (Network ID, Default Gateway IP, Azure DNS reserved-1, Azure DNS reserved-2) and the last 1 (Network broadcast address) IP addresses.
Based on Azure VMet - How small and how large can VNets and subnets be?, The smallest supported IPv4 subnet is /29, and the largest is /2 (using CIDR subnet definitions). IPv6 subnets must be exactly /64 in size.
Special Thanks to davidc + ChatGPT