0.0.0.0/8 — "this network", source only
0.0.0.0/8 — every address from 0.0.0.0 to 0.255.255.255 — is reserved to mean "this network". The designation goes back to RFC 791 in 1981 and was tightened by RFC 1122: these addresses may identify a host on the local network only, and even then only as a source while that host is still figuring out who it is.
No router should ever forward a packet to or from 0.x, and no host should be configured with one. It is the purest bogon in IPv4: any 0.x packet that arrives at your border is either a booting neighbor or a lie.
| Range start | 0.0.0.0 |
| Range end | 0.255.255.255 |
| Subnet mask | 255.0.0.0 |
| Wildcard mask | 0.255.255.255 |
| Total addresses | 16,777,216 |
Shown as range boundaries: 0.0.0.0/8 is reserved "this network" space (RFC 791/1122) with no host assignments, so network/broadcast/usable math is not meaningful.
Bootstrap-only addressing
The one legitimate use is a machine that has no address yet. A fresh DHCP client sends its Discover from source 0.0.0.0 to the limited broadcast address, because it literally cannot put anything else in the field. The moment the lease is granted, 0.0.0.0 disappears from its stack. Addresses like 0.0.1.7 exist on paper as "host 1.7 on this network", but nothing modern uses that form.
Never routable, always filtered
RFC 1122 forbids routers from forwarding 0/8 packets outside the bootstrap case, and every sane edge policy drops them outright. That is why 0.0.0.0/8 anchors every bogon and martian filter list: it can never appear legitimately on a link you do not control, so blocking it costs nothing.
You also meet it in ACLs as a notation trap: 0.0.0.0/8 in a rule names just this reserved slice, while 0.0.0.0/0 matches everything. Mixing those two up in a firewall config is a rite of passage.
CIDR Calculator
Run the math on 0.0.0.0/8 — or any other block
Frequently asked questions
What is the 0.0.0.0/8 range used for?
It is reserved as "this network" (RFC 791/1122). Its only real-world use is as a source address while a host boots without an address — most visibly the 0.0.0.0 source on DHCP Discover packets.
Is 0.1.2.3 a usable IP address?
No. Everything in 0.0.0.0/8 is reserved and unroutable; operating systems refuse to assign it and routers drop the traffic.
Why do I see 0.0.0.0 in my firewall logs?
Usually a device on your LAN mid-DHCP, or spoofed scanner traffic your border should have dropped. On the open Internet, 0.x sources are classic martian packets.
Is 0.0.0.0/8 the same as 0.0.0.0/0?
No. The /8 is the 16.7-million-address "this network" reservation. The /0 is the default route — zero network bits matching the entire IPv4 space.