SubnetPad

/30 Subnet Calculator

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A /30 block contains 4 addresses with 2 usable. It is the traditional choice for point-to-point links between routers because you only need two host addresses — one for each end of the link.

/1
/32

/30 = mask 255.255.255.252 • 2 usable addresses

Results for 192.168.1.0/30

Private (RFC 1918)Class C
Network addressThe first address — identifies the subnet itself
Broadcast addressThe last address — used to reach every device at once
Subnet maskSame as /30 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 hosts4 total addresses in this subnet
More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown

Neighboring /30 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 address11000000.10101000.00000001.00000000
Subnet mask11111111.11111111.11111111.11111100
Network11000000.10101000.00000001.00000000
Broadcast11000000.10101000.00000001.00000011

Quick facts for /30

/30 reference guideBit split, overview, sizing tables, notable networks, and FAQ

Binary bit split

Network bits (30)Host bits (2)
Network bits
30
Host bits
2
Subnet mask
255.255.255.252
Wildcard mask
0.0.0.3
Total addresses
4
Usable hosts
2
Hosts formula
2^2 − 2
/24 relationship
64 fit per /24

Overview

A /30 block contains 4 addresses with 2 usable. It is the traditional choice for point-to-point links between routers because you only need two host addresses — one for each end of the link.

Common use cases

  • Point-to-point router WAN links
  • ISP customer handoff connections
  • VPN tunnel addressing
  • Lab links between routers (CCNA, CCIE)

Subnet sizing reference

Divide /30 into…

PrefixSubnetsHosts each
/3122
/3241

/30 fits inside…

SupernetHosts/30s inside
/2962
/28144
/27308
/266216

Notable /30 networks

  • 10.0.0.0/30.0–.3 (2 usable: .1 and .2)
  • 192.168.1.0/30Classic p2p link example

Frequently asked questions

Common questions about /30 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