More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown
Neighboring /0 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
00000000.00000000.00000000.00000000Network
00000000.00000000.00000000.00000000Broadcast
11111111.11111111.11111111.11111111Quick facts for /0
- Subnet mask: 0.0.0.0
- Wildcard: 255.255.255.255
- Usable hosts: 4,294,967,294
- Total addresses: 4,294,967,296
/0 reference guideBit split, overview, sizing tables, notable networks, and FAQ
Binary bit split
00000000·00000000·00000000·00000000
Network bits (0)Host bits (32)
- Network bits
- 0
- Host bits
- 32
- Subnet mask
- 0.0.0.0
- Wildcard mask
- 255.255.255.255
- Total addresses
- 4,294,967,296
- Usable hosts
- 4,294,967,294
- Hosts formula
- 2^32 − 2
- /24 relationship
- 16,777,216 × /24 networks
Overview
A /0 block covers the entire IPv4 address space — all 4,294,967,296 addresses. It is used in default routing (the "default route") to match any destination when no more specific route exists.
Common use cases
- Default route (0.0.0.0/0) in routing tables
- Catch-all firewall rules
- BGP default route injection
- VPN split-tunneling: route all traffic through the tunnel
Subnet sizing reference
Notable /0 networks
0.0.0.0/0Default route — entire IPv4 space
Frequently asked questions
Common questions about /0 networks, subnet masks, and use cases.