10.0.0.0/8: The Largest Private Range

10.0.0.0/8 is the biggest of the three RFC 1918 private ranges: every address from 10.0.0.0 to 10.255.255.255, about 16.7 million in total. Most enterprise networks and cloud VPCs live somewhere inside it.

10.0.0.0/8 at a glance

Address range
10.0.0.0 – 10.255.255.255
Usable hosts
16,777,214
Total addresses
16,777,216
First usable
10.0.0.1
Last usable
10.255.255.254
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255
Type
Private (RFC 1918)

Is an address inside 10.0.0.0/8?

Yes — 10.42.7.19 is inside 10.0.0.0/8. It is address number 2,754,323 in the block (counting from 0).

What 10.0.0.0/8 is

Any organisation can use 10.0.0.0/8 internally without asking anyone. Because everyone can, everyone does — which is the source of most overlap problems.

The whole /8 is far too big for one network. It is an address plan: you split it by region, site or cloud, then into subnets.

Who uses it

  • Enterprises

    Large companies typically give each site or region a /16 or larger, e.g. 10.1.0.0/16 for HQ and 10.2.0.0/16 for a branch.

  • Cloud VPCs and VNets

    AWS, Azure and Google Cloud all suggest 10.x ranges by default (AWS's VPC wizard offers 10.0.0.0/16). Google Cloud auto-mode VPCs use 10.128.0.0/9.

  • Home ISPs

    Some ISP gateways use 10.0.0.0/24 for the home LAN — Comcast Xfinity routers default to 10.0.0.1.

Conflicts and gotchas

  • Mergers and partners. Two companies that both used 10.0.0.0/8 freely will overlap somewhere. Plan with gaps and document who owns which block.
  • Cloud defaults. Every team that clicks "create VPC" gets 10.0.0.0/16. Peering two of them is impossible. Keep a central list and check with the overlap checker.
  • Broad allow rules. A firewall rule for 10.0.0.0/8 trusts every internal network, including guest Wi-Fi, labs and VPN users. Prefer specific subnets.

How to split 10.0.0.0/8

Worked example: into /12s

  1. Going from /8 to /12 borrows 12 − 8 = 4 bits from the host part.
  2. Each borrowed bit doubles the number of subnets: 24 = 16 subnets.
  3. Each /12 keeps 32 − 12 = 20 host bits: 220 = 1,048,576 addresses, so 1,048,574 usable after removing network and broadcast.
  4. The new mask is 255.240.0.0, so subnets step by 16 in the second octet: 10.0.0.0/12, 10.16.0.0/12, 10.32.0.0/12 … up to 10.240.0.0/12.
Ways to split 10.0.0.0/8
Split into Subnets Usable each First blocks Good for
/12 16 1,048,574 10.0.0.0/12, 10.16.0.0/12, … 16 regions or business units, each 1M addresses.
/16 256 65,534 10.0.0.0/16, 10.1.0.0/16, … 256 sites or VPCs, each 65,536 addresses.
/24 65,536 254 10.0.0.0/24, 10.0.1.0/24, … 65,536 VLAN-sized subnets.

10.0.0.0/8 FAQ

What is the range of 10.0.0.0/8?

10.0.0.0 to 10.255.255.255, which is 16,777,216 addresses (16,777,214 usable as one block).

Is 10.0.0.0/8 private?

Yes. It is one of the three private ranges defined in RFC 1918, alongside 172.16.0.0/12 and 192.168.0.0/16.

What is the subnet mask for 10.0.0.0/8?

255.0.0.0, with wildcard 0.255.255.255. Only the first octet (10) is fixed; the other three can be anything.

Related tools

CIDR to IP Range Every address in 10.0.0.0/8 CIDR Calculator Split 10.0.0.0/8 into any size Subnet Overlap Checker Check it against your other ranges VLSM Calculator Split it into different-sized subnets /8 explained Mask, block size and maths for any /8

Other well-known networks: 10.0.0.0/24, 100.64.0.0/10, 127.0.0.0/8, 169.254.0.0/16, 172.16.0.0/12, 172.17.0.0/16, 192.168.0.0/16, 192.168.0.0/24, 192.168.1.0/24 · all networks