The following public IP prefix sizes are available: /28 (IPv4) or /124 (IPv6) = 16 addresses /29 (IPv4) or /125 (IPv6) = 8 addresses /30 (IPv4) or /126 (IPv6) = 4 addresses /31 (IPv4) or /127 (IPv6) = 2 addresses Prefix size is specified as a Classless Inter-Domain Routing (CIDR) mask size. Reference: https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/public-ip-address-prefix