Nota: Este artículo fue publicado originalmente en 2011 and has been updated with additional context on modern networking practices. The RFC 1918 address ranges themselves have not changed.
Introducción
Private network segments are IP address ranges reserved for use within internal networks that are not directly routable on the public internet. Defined by RFC 1918 (published in 1996), these address spaces allow organizations of any size to build internal networks without consuming globally unique public IP addresses.
Understanding private IP ranges is fundamental knowledge for network administrators, system administrators, and anyone working with routing tables, firewalls, VPNs, or cloud infrastructure. This guide provides a complete reference for private network addressing, including CIDR notation, subnet masks, and practical guidance for choosing the right range.
RFC 1918 Private Address Ranges
The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks for private network use:
| Range | CIDR Notation | Subnet Mask | Available Addresses | Class |
|---|---|---|---|---|
| 10.0.0.0 — 10.255.255.255 | 10.0.0.0/8 | 255.0.0.0 | 16,777,214 | Class A |
| 172.16.0.0 — 172.31.255.255 | 172.16.0.0/12 | 255.240.0.0 | 1,048,574 | Class B |
| 192.168.0.0 — 192.168.255.255 | 192.168.0.0/16 | 255.255.0.0 | 65,534 | Class C |
Importante: The “Available Addresses” count excludes the network address and broadcast address for each range.
Understanding CIDR Notation and Subnet Masks
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by a number to indicate how many bits of the IP address are used for the network portion. The remaining bits are available for host addresses.
Subnet Mask Reference Table
| Address Class | Subnet Mask in Binary | CIDR Prefix | Decimal Equivalent |
|---|---|---|---|
| Class A | 11111111 00000000 00000000 00000000 | /8 | 255.0.0.0 |
| Class B | 11111111 11111111 00000000 00000000 | /16 | 255.255.0.0 |
| Class C | 11111111 11111111 11111111 00000000 | /24 | 255.255.255.0 |
Common Subnet Sizes
Here is a quick reference for the most commonly used subnet sizes within private ranges:
| CIDR | Subnet Mask | Usable Hosts | Typical Use |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,214 | Large enterprise network |
| /16 | 255.255.0.0 | 65,534 | Campus or datacenter segment |
| /20 | 255.255.240.0 | 4,094 | Large VLAN or cloud VPC subnet |
| /24 | 255.255.255.0 | 254 | Standard office LAN segment |
| /28 | 255.255.255.240 | 14 | Small DMZ or management subnet |
| /30 | 255.255.255.252 | 2 | Point-to-point router link |
| /32 | 255.255.255.255 | 1 | Loopback or host route |
Choosing the Right Private Range
10.0.0.0/8 — Best for Large Networks
The 10.x.x.x range provides the most addresses and is the preferred choice for:
- Enterprise networks with thousands of hosts
- Cloud providers (AWS, Azure, and GCP VPCs commonly default to 10.x.x.x)
- Networks requiring extensive subnetting
- Data center environments
Example subnetting scheme:
10.1.0.0/16 -- Production environment
10.2.0.0/16 -- Development environment
10.3.0.0/16 -- Staging environment
10.10.0.0/16 -- Management network172.16.0.0/12 — Best for Medium Networks
The 172.16.x.x through 172.31.x.x range is well suited for:
- Medium-sized businesses
- Secondary network ranges (when 10.x.x.x is already in use)
- Docker default bridge networks (Docker uses 172.17.0.0/16 by default)
- Environments requiring separation from 10.x.x.x ranges used by VPN partners
192.168.0.0/16 — Best for Small Networks
The 192.168.x.x range is most commonly used in:
- Home networks (most consumer routers default to 192.168.0.x or 192.168.1.x)
- Small office / home office (SOHO) environments
- Lab and testing environments
- Individual VLAN segments within larger networks
How Private Addressing Works with NAT
Private IP addresses cannot be routed on the public internet. To allow devices on a private network to access external resources, Network Address Translation (NAT) is used. NAT translates private addresses to a public IP address at the network edge (typically the router or firewall).
The basic flow is:
- A device with private IP
192.168.1.100sends a request to a public website - The router replaces the source address with its public IP (e.g.,
203.0.113.5) and records the mapping - The response from the internet arrives at the router’s public IP
- The router translates the destination back to
192.168.1.100and forwards it internally
Common NAT types include:
- SNAT (Source NAT) — translates the source address of outbound packets
- DNAT (Destination NAT) — translates the destination address of inbound packets (used for port forwarding)
- PAT (Port Address Translation) — maps multiple private addresses to a single public IP using different port numbers (the most common form in home and small office routers)
Verifying Your Network Configuración
On Windows
ipconfig /allOn Linux / macOS
ip addr show # Linux
ifconfig # macOS / older LinuxChecking the Routing Table
# Linux
ip route show
# Windows
route print
# macOS
netstat -rnSolución de Problemas Tips
- Overlapping subnets — If you are merging networks or setting up a VPN and both sides use the same private range, you will experience routing conflicts. Plan your IP addressing to avoid overlap, or use NAT on both ends to remap addresses.
- Incorrect subnet mask — An overly broad or narrow subnet mask will cause devices to either see too many or too few neighbors on the local network. Verify the mask matches your intended subnet size.
- DHCP exhaustion — If you are running out of addresses in a /24 subnet (254 hosts), either expand the subnet or create additional VLANs with their own subnets.
- Cloud VPC CIDR conflicts — When peering VPCs or connecting cloud networks to on-premises, ensure CIDR blocks do not overlap.
Resumen
The three RFC 1918 private address ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — are the foundation of virtually every internal network. Choosing the right range and subnet size depends on the scale of your network, future growth plans, and integration requirements with VPNs or cloud providers. Proper planning of your IP addressing scheme avoids costly renumbering projects and routing conflicts down the road.