How many usable hosts does a /30 subnet have?

A /30 subnet has exactly 2 usable host addresses out of 4 total IPs. The network address and broadcast address each consume one IP, leaving two usable addresses — one for each end of a point-to-point link.

What is the subnet mask for a /30 network?

The subnet mask for a /30 network is 255.255.255.252. In binary, 30 bits are set to 1 followed by 2 bits of 0: 11111111.11111111.11111111.11111100.

How many /30 subnets fit inside a /24 network?

A /24 network can be divided into 64 subnets of /30 size. The difference in prefix length is 30 - 24 = 6 bits, and 2^6 = 64. For example, 10.0.0.0/24 contains 10.0.0.0/30, 10.0.0.4/30, 10.0.0.8/30, through 10.0.0.252/30.

What is a /30 Subnet?

Last reviewed: May 2026

A /30 subnet contains 4 total IP addresses and 2 usable host addresses. The "/30" prefix means 30 bits are used for the network portion, leaving just 2 bits (2² = 4) for host addressing. The /30 is the traditional choice for point-to-point WAN links — exactly two usable addresses, one for each end of the connection.

Calculate any /30 subnet instantly →

Quick Facts: 10.0.0.0/30 Subnet mask: 255.255.255.252 · Wildcard: 0.0.0.3 · Network: x.x.x.0 (on 4-boundary) · Broadcast: x.x.x.3 · Total IPs: 4 · Usable hosts: 2

Full Breakdown

Property	Value
Prefix length	/30
Subnet mask	255.255.255.252
Wildcard mask	0.0.0.3
Total addresses	4
Usable host addresses	2
Network address	x.x.x.0 (must align to multiples of 4: .0, .4, .8, …)
Broadcast address	x.x.x.3 (last address in the block)
Binary mask	11111111.11111111.11111111.11111100

Why /30 for Point-to-Point Links?

A point-to-point link connects exactly two devices — for example, a router on each side of a WAN circuit, or two routers connected over a leased line. You need only two IP addresses: one for each router interface. The /30 wastes minimal address space (2 IPs for network and broadcast) while giving you exactly the 2 usable addresses you need.

Common real-world examples:

WAN links between branch office and HQ routers — each router gets one IP in the /30
Router-to-router connections in OSPF/BGP networks — each interface in the /30 becomes a BGP peer address
VPN tunnel endpoints — the local and remote ends of a site-to-site VPN tunnel
ISP hand-off connections — ISPs frequently assign /30 blocks to customers for the WAN interface IP and gateway IP

/31 as a more efficient alternative (RFC 3021)

RFC 3021 (published 2000) allows /31 for point-to-point links. A /31 has only 2 IPs and eliminates the network and broadcast addresses entirely — both IPs are usable host addresses. This saves 2 IPs compared to /30. Modern routers (Cisco IOS, Juniper JunOS) support /31. Use /30 when working with older equipment or ISPs that don't support /31.

AWS Warning: /30 is Not Recommended in AWS VPC

In an AWS VPC, AWS reserves 5 IPs per subnet. A /30 has only 4 total IPs — all 4 would be consumed by AWS reservations, leaving 0 usable IPs for instances. The minimum usable subnet in AWS is /28. Do not use /29 or /30 in AWS VPC.

Comparison: /30 vs Nearby Prefix Lengths

CIDR	Subnet Mask	Total IPs	Usable Hosts	Typical Use
/29	255.255.255.248	8	6	Very small segment / management VLAN
/30	255.255.255.252	4	2	Point-to-point WAN links — traditional choice
/31	255.255.255.254	2	2*	Point-to-point WAN links — RFC 3021, no wasted IPs

* /31 has no network or broadcast address per RFC 3021 — both IPs are host addresses.

How Many /30 Subnets Fit in a /24?

A /24 block contains 2^(30−24) = 64 subnets of /30 size. For example, 10.0.0.0/24 can be subdivided into 10.0.0.0/30, 10.0.0.4/30, 10.0.0.8/30, … 10.0.0.252/30. Each block starts on a multiple of 4.

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