How many IPs are in a /29? Subnet sizes and what extra IPv4 costs

A /29 has 8 IPv4 addresses. How many of them you can put to work depends on how the block reaches your server: 6 on a normal subnet, usually 5 once the gateway takes one, and all 8 if the block is routed to you. So the honest answer to “how many IP addresses are in a /29” is eight, with an asterisk, and the asterisk is worth sorting out before you pay.

The math in one line

An IPv4 address is 32 bits. The number after the slash says how many of those bits are fixed as the network, and the rest are yours. A /29 leaves 3 host bits, and 2 to the power of 3 is 8.

The mask is 255.255.255.248, and /29 blocks always start on a multiple of 8 in the last octet: .0, .8, .16 and so on up to .248.

Here’s one worked through, using 203.0.113.8/29 from the range RFC 5737 sets aside for documentation:

• 203.0.113.8 is the network address
• 203.0.113.9 through .14 are the six usable host addresses
• 203.0.113.15 is the broadcast address

If the provider’s router sits on .9, your servers get .10 through .14. Five.

Usable IPs by subnet size

The “on-link” column follows RFC 1878: the all-zeros and all-ones addresses are reserved, so you lose two. That count still includes the gateway, so subtract one more if the provider’s router lives inside your block. The last column is the add-on price from every GigeNET dedicated server order form and what it gets you on that server.

The /31 is the odd one. RFC 3021 says that on a point-to-point link with a 31-bit mask, both addresses “MUST be interpreted as host addresses,” because there’s nobody else on the link to broadcast to.

On-link or routed: ask before you configure

The two delivery methods give you different counts for the same price.

On-link. The block lives on your server’s network segment like a small LAN. Your interface takes addresses from it, the gateway is one of them, and the network and broadcast addresses are off-limits. A /29 gives you 5 or 6. This is the easy setup for a hypervisor, because you can bridge VMs straight onto the segment.

Routed. The provider points the whole block at your server’s main IP, and your server decides what to do with it. There’s no shared segment, so there’s nothing to broadcast to and no gateway inside the block, and you can usually use all 8. The trade-off is that your server has to route, so VMs need a routed setup on the host instead of a plain bridge.

Neither is wrong. They’re just different numbers, and you want to know which one you’re getting before you write the config or promise a customer five addresses.

Here’s how ours work. On a GigeNET dedicated server, add-on blocks are routed to your server’s link IP, so there’s no gateway inside the block and all 8 addresses of a /29 (or all 16 of a /28) are yours to use. On colocation the block is on-link, so a /29 gives you 5 usable addresses once the network, broadcast and gateway addresses are taken; if you run your own router, you can take the block as routed and carve it up however you like. The smaller options on the dedicated order forms, 1, 2 or 4 IPs, add that many addresses to the server.

Why you’d need more than one IP

SSL used to require it. Before Server Name Indication, the browser only said which site it wanted after the TLS handshake, by which point the server had already picked a certificate, so every HTTPS site needed its own address. RFC 6066 fixed that by letting the client name the site up front, and modern browsers all send it. One IP can serve hundreds of HTTPS sites now. If someone tells you to buy an IP per certificate, they’re about a decade behind.

Nameservers. Running your own ns1 and ns2 means two addresses at minimum, and ideally on different networks so one outage doesn’t take both down. Our post on whether to run your own nameserver covers when that’s worth the trouble.

Mail reputation. This is the strongest reason left. Google’s email sender guidelines say a sending IP “must have a corresponding PTR record,” and that if you send from more than one address you should “use a different IP address for each message type.” Receipts on one IP and newsletters on another means a bad campaign doesn’t sink your password-reset emails.

Multi-tenant and virtual machines. A Proxmox server running six public-facing VMs needs six public addresses, unless they all sit behind one reverse proxy. Resellers often give each client their own IP, and two services that both insist on the same port need two IPs.

IPv6, the free alternative. A single IPv6 /64 holds about 18 quintillion addresses, so nobody rations them the way IPv4 is rationed. AWS has charged $0.005 per hour for every public IPv4 address since February 1, 2024 (AWS announcement), about $3.65 a month each. The catch is reach: roughly half of Google’s users connect over IPv6, per the figures in our IPv4 vs IPv6 guide, so anything public still needs an IPv4 address. My rule is to put IPv6 everywhere you can and buy IPv4 only for what has to face IPv4-only users.

Why your host asks what the addresses are for

In the US and Canada, IPv4 space comes from ARIN, and ARIN’s Number Resource Policy Manual puts the paperwork on your provider. Section 4.2.3.1 says ISPs “should have documented justification available for each reassignment and reallocation.” Section 4.2.3.7.1 says every reassignment of a /29 or more “shall be registered in the WHOIS directory via SWIP,” including the client’s organizational information. And under 4.2.4.1, a provider has to have used at least 80% of its space before ARIN gives it more.

So expect a question when you order. Have one line per address ready: three VMs, two nameservers, one mail IP. A /28 “for later” is the kind of request that gets questioned.

One more rule people miss. Section 4.2.3.3 recommends that a customer who leaves “return the network addresses to the ISP and renumber.” Rented IPs normally stay with the host, so lower your DNS TTLs before any move.

What extra IPv4 costs in 2026

On GigeNET dedicated servers it’s $2 per IP per month with no setup fee, from a single /32 at $2 up to a /28 at $32, right on the order form. Anything bigger than a /28 goes through a custom quote.

Buying is a different market. The ip4.market price index (updated September 28, 2026) puts the 90-day median at $25.50 per address for a /24, falling to $15.75 at a /20 and $12.38 at a /16. CircleID’s first-half 2026 review found an average of $20.04 per address, down 35.7% from a year earlier.

You can’t buy a /29, though. ARIN’s minimum transfer size is a /24, so the smallest purchase is 256 addresses, roughly $5,100 to $6,500 at those prices, and then someone has to announce it: your own ASN and upstreams, or a host willing to route it for you. Below a /24, renting from your host is the only practical option, and at $16 a month for a /29 it’s the cheap one.

FAQ

Every GigeNET dedicated server order form has the IPv4 add-on built in, from one address to a /28. Need more than 16? Send the details through the custom quote form and we’ll reply with a configuration and a price.