IP Addressing Plan Template

Why Document Your IP Plan?

An IP addressing plan is the single most important network document. Without it, teams make conflicting assignments, subnets overlap, and troubleshooting becomes guesswork.

A good IP plan answers:

• What subnets exist and where?
• Who owns each allocation?
• What is reserved for growth?
• How do sites interconnect?

Plan Structure

An enterprise IP plan should have four sections:

1. Site Summary

2. Subnet Detail

For each site, document every subnet:

Site: HQ (10.1.0.0/16)
------------------------------------------------------
Subnet            VLAN  Name          Hosts  Gateway
10.1.1.0/24       10    Corporate     254    10.1.1.1
10.1.2.0/24       20    Engineering   254    10.1.2.1
10.1.3.0/24       30    VoIP          254    10.1.3.1
10.1.4.0/24       40    Guest-WiFi    254    10.1.4.1
10.1.10.0/24      100   Servers       254    10.1.10.1
10.1.11.0/24      101   Database      254    10.1.11.1
10.1.254.0/28     999   Management    14     10.1.254.1
10.1.255.0/30     --    WAN to DC     2      10.1.255.1

3. Reserved Ranges

Always document what is intentionally unallocated:

10.1.5.0/24  -- 10.1.9.0/24     Reserved for future VLANs
10.1.12.0/24 -- 10.1.253.0/24   Reserved for growth
10.0.0.0/16                      Reserved (do not use)

4. Allocation Policy

Define rules before anyone starts assigning:

• Gateways always use .1 in every subnet
• Static servers use .10 -- .49
• DHCP pools start at .50
• Point-to-point WAN links use /30 or /31
• New sites get a /16 from the 10.x.0.0 range
• VPN pools must not overlap with any site

IPAM Tools

For organizations beyond 5 subnets, a spreadsheet becomes error-prone. Use an IP Address Management (IPAM) tool:

Versioning and Reviews

Treat your IP plan like code:

• Store it in version control (Git)
• Require peer review for changes
• Run automated validation to catch overlaps
• Review the full plan quarterly