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Network Engineering · Zero Trust Architecture

CIDR Subnet & Microsegmentation IP Calculator

Compute IPv4 network boundaries, usable host address ranges, wildcard masks, and 32-bit binary octet divisions. Automatically split parent CIDR blocks into 4-tier Zero Trust microsegmented subnets for cloud VPCs, AWS security groups, and enterprise firewalls.

Privacy guarantee: Evaluated 100% in local browser memory. IP addresses and subnets are never logged or transmitted.
Common Architecture Presets:
Network Base CIDR
10.0.0.0/22
Usable Hosts: 1,022
Total IP Block: 1,024
Subnet Mask
255.255.252.0
0xFFFFFC00
Cisco Wildcard Mask
0.0.3.255
Inverted bitmask
Broadcast Address
10.0.3.255
Subnet ceiling
Usable Host Address Range:
10.0.0.1 - 10.0.3.254
32-Bit Binary Mask Division (Network vs Host Bits)■ Network■ Host

Zero Trust 4-Tier Microsegmentation Split

When architecting cloud VPCs or enterprise VLANs, best practices mandate isolating tiers into distinct security boundaries. Here is how this CIDR block subdivides into 4 equal subnets:

Architectural TierSubnet CIDRHost RangeCapacity
AWS VPC Route Table Entry
Destination: 10.0.0.0/22 -> Target: vpc-peering / transit-gateway
Cisco IOS Subnet Route
ip route 10.0.0.0 255.255.252.0 GigabitEthernet0/1

Understanding Classless Inter-Domain Routing (CIDR)

Classless Inter-Domain Routing (CIDR) was introduced in 1993 (RFC 1519) to replace the rigid Class A, B, and C IPv4 network architecture. Instead of fixed byte boundaries, CIDR notation appends a slash followed by the prefix length (e.g. /24), indicating how many of the 32 bits represent the network prefix.

Why Subnet Capacity is Always Total IPs Minus 2

In any IPv4 subnet with a prefix of /30 or shorter, two IP addresses are reserved by the networking standard:

  • Network Address (All Host Bits 0): Identifies the subnet itself and cannot be assigned to a network interface.
  • Broadcast Address (All Host Bits 1): Sends packets to all hosts on the subnet simultaneously.

Therefore, usable host capacity is calculated as 2^(32 - Prefix) - 2. For example, a /24 contains 256 total IP addresses but only 254 usable host addresses.

Zero Trust Microsegmentation Best Practices

In legacy network designs, any endpoint connected to a corporate VPN or local LAN could communicate directly with all other devices. Under modern Zero Trust architecture, networks are partitioned into isolated microsegments where lateral movement is blocked by default:

  1. Public DMZ: Only hosts load balancers and ingress reverse proxies. Direct access to database subnets is strictly forbidden.
  2. Application Tier: Private compute instances accessible only from the reverse proxy over specified application ports.
  3. Data Tier: High-security database and immutable storage clusters isolated from all internet routing.
  4. Management Tier: Dedicated bastion hosts or identity-aware Zero Trust Network Access (ZTNA) connectors.
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