SubnetPad

/3 Subnet Calculator

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A /3 block contains 536,870,912 addresses. Used by very large ISPs and in BGP route aggregation at the global routing table level.

/1
/32

/3 = mask 224.0.0.0 • 536,870,910 usable addresses

Results for 0.0.0.0/3

Reserved (this network)Class A
Network addressThe first address — identifies the subnet itself
Broadcast addressThe last address — used to reach every device at once
Subnet maskSame as /3 in CIDR notation
First usable hostThe first IP you can assign to a device
Last usable hostThe last IP you can assign to a device
Usable hosts536,870,912 total addresses in this subnet
More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown

Neighboring /3 subnets

Wildcard mask
Used in Cisco ACLs and OSPF
CIDR notation
IP in hexadecimal
IP as 32-bit integer
Reverse DNS (PTR)
Host bits / subnet bits

Binary breakdown

IP address00000000.00000000.00000000.00000000
Subnet mask11100000.00000000.00000000.00000000
Network00000000.00000000.00000000.00000000
Broadcast00011111.11111111.11111111.11111111

Quick facts for /3

/3 reference guideBit split, overview, sizing tables, notable networks, and FAQ

Binary bit split

Network bits (3)Host bits (29)
Network bits
3
Host bits
29
Subnet mask
224.0.0.0
Wildcard mask
31.255.255.255
Total addresses
536,870,912
Usable hosts
536,870,910
Hosts formula
2^29 − 2
/24 relationship
2,097,152 × /24 networks

Overview

A /3 block contains 536,870,912 addresses. Used by very large ISPs and in BGP route aggregation at the global routing table level.

Common use cases

  • Tier-1 ISP route aggregation
  • Regional backbone address planning
  • IANA and RIR address block management

Subnet sizing reference

Divide /3 into…

PrefixSubnetsHosts each
/42268,435,454
/54134,217,726
/6867,108,862
/71633,554,430

/3 fits inside…

SupernetHosts/3s inside
/21,073,741,8222
/12,147,483,6464
/04,294,967,2948

Frequently asked questions

Common questions about /3 networks, subnet masks, and use cases.

All CIDR prefix sizes

/0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32