IPv4 Subnets Explained: /31, /30, /29, /28, /27, /26 (How Many IPs You Can Actually Use)

When you order “extra IPv4” you’re really ordering an IP block (also called a subnet), like /30 or /29. Clients often ask: “How many IPs can I use for my server and applications?” This article answers that clearly, including the common “gateway” confusion.

Quick chart: total IPs vs IPs you can use on your server

In most real-world setups, one IP is used as the gateway (the router address your server uses to reach the internet). That gateway IP is not an extra third IP — it usually comes from inside the block.

* Typical = “gateway is inside the block.” Some networks can be set up differently (see “Advanced note” below).

What is a gateway (and why can’t I use it for hosting)?

Think of the gateway as your server’s “next hop” to the internet.

• Your server needs a gateway to reach anything outside its own subnet (websites, updates, APIs, etc.).

• The gateway is usually an IP address on the provider’s router.

• Because it belongs to the router, you can’t bind it on your server to host websites, game servers, or other apps.

Bottom line: The gateway is required for normal internet connectivity, and it usually consumes one of the host IPs in small blocks like /31 and /30.

Why a /30 doesn’t usually mean “2 IPs for my apps”

A /30 contains:

• 2 host IPs

• But one host IP is typically the gateway

• That leaves 1 IP for your server/apps

Example (illustration):

• Block: 203.0.113.8/30

• Host IPs: 203.0.113.9 and 203.0.113.10

• Typical setup:

  • 203.0.113.9 = gateway (router)

  • 203.0.113.10 = your server IP (usable for apps)

So yes: /30 has 2 host IPs, but you typically only get 1 IP you can use on your server.

What about /31 — why would anyone order it?

A /31 is commonly used for a simple “link” where:

• 1 IP is used by the gateway/router

• 1 IP is used by your server

So in practice, a /31 is usually “one server IP” (with the other IP being the gateway).

Which block size should I choose?

Use this quick guide (based on typical gateway-inside-block setups):

• Need 1 usable IPv4 for the server? → /31 or /30

• Need ~5 usable IPv4s for apps, containers, VIPs, or NAT? → /29

• Need ~13 usable IPv4s → /28

• Need ~29 usable IPv4s → /27

• Need ~61 usable IPv4s → /26

If you’re not sure: /29 is often the first size that feels “roomy” for real projects because it gives multiple assignable IPs.

Common questions (FAQ)

“Sales told me /30 has 2 usable IPs. Support says I only get 1. Who’s right?”

Both, depending on what “usable” means:

• Subnet math: /30 has 2 host IPs

• Typical customer usage: 1 is the gateway, leaving 1 IP you can assign on your server

“Can I host a website or game server on the gateway IP?”

No. The gateway IP normally belongs to the network router, not your server.

“Do I always need a gateway?”

If you want normal internet access: yes (you need a default route).
Without a gateway, your server can only talk to IPs inside the same subnet.

“Do I need multiple IPs to host multiple websites?”

Usually no. Most sites can share a single IP using modern HTTPS (SNI).
You typically need multiple IPs for things like:

• Multiple servers/VMs that each need their own public IP

• Certain legacy apps requiring a dedicated IP

• Special routing/NAT/VIP designs

Advanced note (for accuracy): routed blocks can change the “usable for you” number

Some providers can route an IP block to you so the gateway is not inside the block. In that design, you may be able to use all host IPs in the block on your side.

If you’re comparing providers or reading older documentation, this is why you may see different answers. For our service, your order details will specify whether your block is gateway-inside-block (most common) or routed.

Summary in one sentence

A block like /30 has 2 host IPs, but in the most common setup one host IP is used as the gateway, so the client typically gets 1 IP they can assign to their server/applications