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CIDR /0Private (RFC 1918)

/0 Subnet Mask (0.0.0.0) - Usable Hosts & CIDR | ipcalc.net

Everything about /0 subnets: Subnet mask 0.0.0.0, wildcard mask 255.255.255.255, 4,29,49,67,294 usable hosts, binary breakdown, and Cisco configuration templates.

Enter any notation: 192.168.1.1/24, 10.0.0.1 255.255.255.0, or plain IP

Subnet Mask Prefix: /0Netmask: 0.0.0.0
Presets:

32-Bit Subnet Boundary Visualizer

Click any bit position to adjust the CIDR prefix boundary

Network (0 bits)
Host (32 bits)
Octet 110Mask: 0
00000000
Octet 20Mask: 0
00000000
Octet 30Mask: 0
00000000
Octet 40Mask: 0
00000000
Usable Hosts
4,294,967,294
Total IPs: 4,294,967,296
Network Address
0.0.0.0
Prefix: /0
Usable Host Range
0.0.0.1
255.255.255.254
Broadcast Address
255.255.255.255
Subnet Broadcast

Detailed Subnet Breakdown

Private (RFC 1918)
Subnet Mask
0.0.0.0
Wildcard Mask (Cisco ACL)
255.255.255.255
Hexadecimal IP / Mask
0x0A000000 / 0x00000000
Integer / Decimal IP
167772160
IP Class & Routing
Class A • Classless Inter-Domain Routing (CIDR)
Reverse DNS (in-addr.arpa)
0.0.0.10.in-addr.arpa
Cisco IOS Command Templates
ip address 10.0.0.0 0.0.0.0
access-list 1 permit 0.0.0.0 255.255.255.255

Technical Subnet Specifications

Prefix Length/0
Dotted Decimal Subnet Mask0.0.0.0
Wildcard Mask (Inverse)255.255.255.255
Total Available IP Addresses4,29,49,67,296
Usable Host Capacity4,29,49,67,294 hosts
Network Bits vs Host Bits0 Network / 32 Host
Binary Subnet Mask00000000.00000000.00000000.00000000

Cisco IOS Configuration

Copy-paste templates for Cisco router and switch interface setup:

! Configure Interface

interface GigabitEthernet0/0/1

ip address 0.0.0.1 0.0.0.0

no shutdown

! Access-Control List

access-list 10 permit 0.0.0.0 255.255.255.255

Tip: Wildcard mask is computed by inverting the subnet mask (~mask).

Typical Network Use Cases for /0

A /0 network block provides 4,29,49,67,296 total IP addresses with 4,29,49,67,294 usable host interfaces.

Designated Role: Default Route / Entire Internet.

Frequently Asked Questions: /0 (0.0.0.0)

Authoritative answers to common /0 subnetting, host capacity, and networking questions.

Q1How many usable hosts are in a /0 subnet?
A /0 subnet provides 4,29,49,67,294 usable host IP addresses out of 4,29,49,67,296 total addresses. In IPv4 networking, 2 addresses are reserved: the network address (0.0.0.0) and the directed broadcast address (255.255.255.255). Formula: 2^(32 - 0) - 2 = 4,29,49,67,294 usable hosts.
Q2What is the subnet mask and wildcard mask for /0?
The dotted-decimal subnet mask for a /0 prefix is 0.0.0.0. The corresponding wildcard mask (used in Cisco ACLs and OSPF network statements) is 255.255.255.255. In binary, the subnet mask consists of 0 network bits (1s) followed by 32 host bits (0s).
Q3What are the network, broadcast, and usable IP ranges for 10.0.0.0/0?
For the 10.0.0.0/0 subnet: the Network Address is 0.0.0.0, the Broadcast Address is 255.255.255.255, and the usable host range extends from 0.0.0.1 through 255.255.255.254. Any host interface configured in this subnet must have an IP within this range and netmask 0.0.0.0.
Q4What is a /0 subnet typically used for in network design?
A /0 subnet is typically deployed for default route / entire internet. In enterprise and cloud environments (such as AWS VPCs or Azure VNets), /0 allocations provide the optimal balance between host capacity and address conservation.
Q5What does /0 mean in CIDR notation?
Classless Inter-Domain Routing (CIDR) notation expresses the subnet mask as a forward slash followed by the prefix length. A /0 prefix indicates that the first 0 bits of the 32-bit IPv4 address are locked for network identification, leaving the remaining 32 bits available for addressing host interfaces.