¿Cómo calculo una subred y genero el inventario?

Escribe una IP y la máscara CIDR, pulsa Calcular y guardar, activa las categorías en el planificador y descarga el Excel. Cada fila es una IP lista para rellenar nombre, usuario y MAC.

¿Puedo combinar varias redes?

Sí. Calcula cada red, márcalas en el historial y usa «Usar seleccionadas en el planificador». Luego eliges en qué red va cada tipo de equipo.

CIDR Subnetting & IP Planning

Calculator of IP Subnets & Network Planner

Calculate IPv4/IPv6 subnets, plan IPs by device type and download Excel inventory.

IP address

Prefix / CIDR: /24

A/B/C are mask shortcuts (/8, /16, /24). Offices usually use C · /24.

IP planner (IPv4)

Pick networks → Auto or manual range → colored Excel (free IPs summarized if many).

Networks in the plan

Check networks to plan.

Calculate an IPv4 network above.

Select at least one network to configure categories.

IP Subnetting Architecture & CIDR

Subnet masks, binary host/network math, RFC 1918 private ranges, and IPv6.

CIDR Fundamentals & Network Splitting

CIDR replaced rigid Class A/B/C addressing. The prefix (/24, /16) denotes the contiguous network bits, allocating the remainder for host addresses.

RFC 1918 Private Ranges & NAT

Ranges 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 are non-routable over the internet, relying on NAT gateways to access public services.

Subnet Mask vs. Wildcard Mask (ACLs)

The subnet mask filters the network portion via bitwise AND. The wildcard mask (inverse of mask) is essential for Cisco Access Control Lists (ACLs) and OSPF.

IPv6 Address Space & Standard /64 Subnets

IPv6 uses 128-bit hexadecimal addressing. Standard local LAN allocations use /64 prefixes, granting 18.4 quintillion addresses per subnet for SLAAC autoconfig.

IP Subnetting & Routing Troubleshooting

Step-by-step fixes for IP conflicts, unreachable gateways, and DHCP pool shortages.

Issue 1

Duplicate IP Address Conflict in Local LAN

⚡ Quick Fix:Run `ipconfig /release && ipconfig /renew` to request a fresh, uncontested lease from DHCP.

🔧 Technical Fix:Reserve static IPs (.1 to .50) outside the active DHCP allocation pool range (.51 to .254) in router settings.

Issue 2

Default Gateway Outside Subnet Boundary

⚡ Quick Fix:Verify both host IP and gateway IP fall within the exact same CIDR boundary.

🔧 Technical Fix:Set gateway to a valid usable host (typically first .1 or last .254), never the network (.0) or broadcast (.255).

Issue 3

DHCP Pool Exhaustion in /24 Subnets

⚡ Quick Fix:Lower DHCP lease time from 24h to 2h to quickly reclaim addresses from transient guest devices.

🔧 Technical Fix:Expand subnet mask from /24 (254 hosts) to /23 (510 hosts, 255.255.254.0) or /22 (1022 hosts, 255.255.252.0).

Issue 4

Inter-VLAN Communication Breakdown

⚡ Quick Fix:Ping the local VLAN gateway to verify Layer 3 switch virtual interfaces (SVI) are up.

🔧 Technical Fix:Enable `ip routing` on Layer 3 switches or configure 802.1Q subinterfaces on the core firewall.

Did You Know? IP Subnetting Trivia

IPv4 exhaustion history, IPv6 cosmic scale, and the 127.0.0.1 loopback origin.

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February 3, 2011: IPv4 Pool Exhaustion

On this date, IANA allocated the final five /8 blocks (16.7M IPs each) to regional registries, formally exhausting global unallocated IPv4 space.

🌌

340 Undecillion IPv6 Addresses (3.4 × 10^38)

IPv6 provides 3.4 × 10^38 addresses. There are enough IPs to assign trillions of addresses to every grain of sand on planet Earth.

🏠

127.0.0.1: Why 16 Million IPs Were Reserved for Localhost

In 1981, RFC 790 reserved the entire 127.0.0.0/8 block (16.7M addresses) for internal loopback. Any address like 127.0.0.2 routes right back to localhost.

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Why We Subtract 2 (Network & Broadcast)

In every IPv4 subnet, all-zeros host bits designate the network ID and all-ones host bits designate the broadcast address, requiring (2^n - 2) usable hosts.