255.0.0.0 Subnet Mask
255.0.0.0 is the subnet mask for a /8 network — 16,777,214 usable hosts out of 16,777,216 addresses.
CIDR Prefix
/8
Wildcard Mask
0.255.255.255
Total Addresses
16,777,216
Usable Hosts
16,777,214
Network Bits
8
Host Bits
24
255.0.0.0 in Binary
Each octet is eight bits. The highlighted bits are the 8 network bits; the rest are the 24 host bits that vary within the subnet.
255
0
0
0
Networks Using 255.0.0.0
| Network | Host Range | Broadcast |
|---|---|---|
| 10.0.0.0/8 | 10.0.0.1 – 10.255.255.254 | 10.255.255.255 |
| 172.0.0.0/8 | 172.0.0.1 – 172.255.255.254 | 172.255.255.255 |
| 192.0.0.0/8 | 192.0.0.1 – 192.255.255.254 | 192.255.255.255 |
Neighbouring Masks
Frequently Asked Questions
What CIDR prefix is 255.0.0.0?
255.0.0.0 is /8 in CIDR notation. The mask sets the first 8 of the 32 bits in an IPv4 address to 1, marking them as the network portion, and leaves the remaining 24 bits as 0 for hosts.
How many hosts does 255.0.0.0 allow?
A network with mask 255.0.0.0 holds 16,777,216 addresses, of which 16,777,214 are usable by hosts — the network address and the broadcast address are reserved.
What is the wildcard mask for 255.0.0.0?
The wildcard mask for 255.0.0.0 is 0.255.255.255. It is the bitwise inverse: every 1 in the subnet mask becomes a 0 and every 0 becomes a 1. Cisco access lists and OSPF network statements take the wildcard form rather than the subnet mask.
Standards
- RFC 950 — Internet Standard Subnetting Procedure
Defines the dotted-decimal subnet mask itself, and the rule that the network and broadcast addresses are not assignable to hosts.
- RFC 4632 — Classless Inter-Domain Routing (CIDR)
Establishes the /8 prefix notation that 255.0.0.0 is equivalent to, and requires masks to be contiguous — which is why exactly 33 of the 4.3 billion possible values are valid.