IPRangeExplorer

128.0.0.0/1

Public

Class B — /1 prefix — 2,147,483,646 usable hosts

Network Address
128.0.0.0
Broadcast Address
255.255.255.255
Subnet Mask
128.0.0.0
Usable Hosts
2,147,483,646
First Usable IP
128.0.0.1
Last Usable IP
255.255.255.254
Total IPs
2,147,483,648
Prefix Length
/1

Network address — the base address of the block (128.0.0.0). All devices in this subnet share this prefix. Cannot be assigned to a host.

Broadcast address — packets sent to 255.255.255.255 are delivered to every device in the subnet. Also reserved — not assignable.

Usable hosts — the 2,147,483,646 addresses between those two that you can assign to servers, VMs, or interfaces.

Subnet mask — 128.0.0.0 is the dotted-decimal equivalent of /1. Older tools and Cisco configs use this format instead of CIDR slash notation.

Full Details

CIDR Notation 128.0.0.0/1
Network Address 128.0.0.0
Broadcast Address 255.255.255.255
Subnet Mask 128.0.0.0
Wildcard Mask 127.255.255.255
Prefix Length /1
IP Address Class Class B
Total IP Addresses 2,147,483,648
Usable Host Addresses 2,147,483,646
First Usable IP 128.0.0.1
Last Usable IP 255.255.255.254
Network (Hex) 0x80000000
Broadcast (Hex) 0xFFFFFFFF
Address Type Public / Globally Routable

Binary Representation

Network Address
10000000.00000000.00000000.00000000
Subnet Mask
10000000.00000000.00000000.00000000

The first 1 bits (1s in the mask) identify the network. The remaining 31 bits identify hosts within the network.

Split into Equal Subnets

Split 128.0.0.0/1 into 2 equal /2 subnets (1,073,741,822 usable hosts each).

# CIDR Network First Usable Last Usable Broadcast Hosts
1 128.0.0.0/2 128.0.0.0 128.0.0.1 191.255.255.254 191.255.255.255 1,073,741,822
2 192.0.0.0/2 192.0.0.0 192.0.0.1 255.255.255.254 255.255.255.255 1,073,741,822

/1 Subnet Reference

Total IPs 2,147,483,648
Usable Hosts 2,147,483,646
Subnet Mask 128.0.0.0
Wildcard 127.255.255.255
Full /1 reference →

Related Ranges

Parent /0 block 0.0.0.0/0 Sibling /1 block 0.0.0.0/1

Adjacent Prefix Sizes

/0 4,294,967,294 hosts /1 2,147,483,646 hosts /2 1,073,741,822 hosts /3 536,870,910 hosts

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