More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown
Neighboring /2 subnets
- Wildcard mask
- Used in Cisco ACLs and OSPF
- CIDR notation
- IP in hexadecimal
- IP as 32-bit integer
- Reverse DNS (PTR)
- Host bits / subnet bits
Binary breakdown
IP address
00000000.00000000.00000000.00000000Subnet mask
11000000.00000000.00000000.00000000Network
00000000.00000000.00000000.00000000Broadcast
00111111.11111111.11111111.11111111Quick facts for /2
- Subnet mask: 192.0.0.0
- Wildcard: 63.255.255.255
- Usable hosts: 1,073,741,822
- Total addresses: 1,073,741,824
/2 reference guideBit split, overview, sizing tables, notable networks, and FAQ
Binary bit split
11000000·00000000·00000000·00000000
Network bits (2)Host bits (30)
- Network bits
- 2
- Host bits
- 30
- Subnet mask
- 192.0.0.0
- Wildcard mask
- 63.255.255.255
- Total addresses
- 1,073,741,824
- Usable hosts
- 1,073,741,822
- Hosts formula
- 2^30 − 2
- /24 relationship
- 4,194,304 × /24 networks
Overview
A /2 block contains 1,073,741,824 addresses — a quarter of the IPv4 address space. Used in ultra-large BGP aggregation and some regional internet registry (RIR) allocations.
Common use cases
- BGP super-aggregation at Tier-1 ISPs
- RIR address space management
- Very large cloud region addressing plans
Subnet sizing reference
Notable /2 networks
0.0.0.0/20–63.x.x.x address range64.0.0.0/264–127.x.x.x address range
Frequently asked questions
Common questions about /2 networks, subnet masks, and use cases.