IPRangeExplorer

151.4.0.0/21

Public

Class B — /21 prefix — 2,046 usable hosts

Network Address
151.4.0.0
Broadcast Address
151.4.7.255
Subnet Mask
255.255.248.0
Usable Hosts
2,046
First Usable IP
151.4.0.1
Last Usable IP
151.4.7.254
Total IPs
2,048
Prefix Length
/21

Network address — the base address of the block (151.4.0.0). All devices in this subnet share this prefix. Cannot be assigned to a host.

Broadcast address — packets sent to 151.4.7.255 are delivered to every device in the subnet. Also reserved — not assignable.

Usable hosts — the 2,046 addresses between those two that you can assign to servers, VMs, or interfaces.

Subnet mask — 255.255.248.0 is the dotted-decimal equivalent of /21. Older tools and Cisco configs use this format instead of CIDR slash notation.

Full Details

CIDR Notation 151.4.0.0/21
Network Address 151.4.0.0
Broadcast Address 151.4.7.255
Subnet Mask 255.255.248.0
Wildcard Mask 0.0.7.255
Prefix Length /21
IP Address Class Class B
Total IP Addresses 2,048
Usable Host Addresses 2,046
First Usable IP 151.4.0.1
Last Usable IP 151.4.7.254
Network (Hex) 0x97040000
Broadcast (Hex) 0x970407FF
Address Type Public / Globally Routable

Binary Representation

Network Address
10010111.00000100 10010111.00000100.00000000.00000000
Subnet Mask
11111111.11111111.11111000.00000000

The first 21 bits (1s in the mask) identify the network. The remaining 11 bits identify hosts within the network.

Split into Equal Subnets

Split 151.4.0.0/21 into 2 equal /22 subnets (1,022 usable hosts each).

# CIDR Network First Usable Last Usable Broadcast Hosts
1 151.4.0.0/22 151.4.0.0 151.4.0.1 151.4.3.254 151.4.3.255 1,022
2 151.4.4.0/22 151.4.4.0 151.4.4.1 151.4.7.254 151.4.7.255 1,022

/21 Subnet Reference

Total IPs 2,048
Usable Hosts 2,046
Subnet Mask 255.255.248.0
Wildcard 0.0.7.255
Full /21 reference →

Related Ranges

Parent /20 block 151.4.0.0/20 Sibling /21 block 151.4.8.0/21

Adjacent Prefix Sizes

/19 8,190 hosts /20 4,094 hosts /21 2,046 hosts /22 1,022 hosts /23 510 hosts

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