Understanding CIDR notation for IPv4 and IPv6 subnets
CIDR (Classless Inter-Domain Routing) notation is a compact method for specifying IP addresses and their routing suffix. This page provides detailed information about the /30 subnet.
Very small network or point-to-point link. These small subnets are often used for point-to-point links between routers or for very specific, isolated services where only one or two hosts are needed.
| CIDR Notation | /30 |
| Subnet Mask | 255.255.255.252 |
| Binary Subnet Mask | 11111111 11111111 11111111 11111100 |
| Total Addresses | 4 |
| Usable Hosts (Standard) | 2 |
| AWS Usable IPs | 0 (5 reserved) |
| Azure Usable IPs | 0 (5 reserved) |
| GCP Usable IPs | 0 (4 reserved) |
Large allocation typically used by regional registries or major ISPs
IPv6 uses a 128-bit address space, a massive increase from IPv4's 32 bits. This allows for approximately 340 undecillion (3.4 x 1038) unique addresses, effectively eliminating the address exhaustion concerns of IPv4.
IPv6 addresses are represented as eight groups of four hexadecimal digits, separated by colons (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). Leading zeros in each group can be omitted, and one sequence of consecutive all-zero groups can be replaced by a double colon (::), for instance 2001:db8::1.