Network Planner
Plan sites and network zones from a parent CIDR block with growth-friendly subnet sizing.
Enter network values
Use the example or enter your own subnet, plan, MAC, or port value.
Results update locally in your browser.
Create a simple multi-site, multi-zone IPv4 network plan with VLAN IDs, subnets, gateways, and DHCP ranges.
Network plan insights
A clean first-pass address plan for sites/zones, with capacity checks before implementation.
8 routed networks allocated from 10.20.0.0/20.
116 target host slots vs 126 usable per zone.
Each zone targets 116 usable slots inside a /25 with 126 usable hosts, so busy zones have limited growth room.
Next: Compare /24 for high-growth zones before assigning DHCP scopes.
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| Option | Prefix | Child subnets in parent | Usable hosts / zone | Parent use | Host target use | Decision note |
|---|---|---|---|---|---|---|
| One size larger | /24 | 16 | 254 | 50% | 46% | Fits entered sites/zones and host target. |
| Recommended | /25 | 32 | 126 | 25% | 92% | Fits entered sites/zones and host target. |
| One size smaller | /26 | 64 | 62 | 13% | 100% | Too little per-zone host capacity. |
| Site / zone | Name | Subnet | Gateway | DHCP range | Usable |
|---|---|---|---|---|---|
| Site 1 / Zone 1 | Site 1 Zone 1 | 10.20.0.0/25 | 10.20.0.1 | 10.20.0.2 – 10.20.0.126 | 126 |
| Site 1 / Zone 2 | Site 1 Zone 2 | 10.20.0.128/25 | 10.20.0.129 | 10.20.0.130 – 10.20.0.254 | 126 |
| Site 1 / Zone 3 | Site 1 Zone 3 | 10.20.1.0/25 | 10.20.1.1 | 10.20.1.2 – 10.20.1.126 | 126 |
| Site 1 / Zone 4 | Site 1 Zone 4 | 10.20.1.128/25 | 10.20.1.129 | 10.20.1.130 – 10.20.1.254 | 126 |
| Site 2 / Zone 1 | Site 2 Zone 1 | 10.20.2.0/25 | 10.20.2.1 | 10.20.2.2 – 10.20.2.126 | 126 |
| Site 2 / Zone 2 | Site 2 Zone 2 | 10.20.2.128/25 | 10.20.2.129 | 10.20.2.130 – 10.20.2.254 | 126 |
| Site 2 / Zone 3 | Site 2 Zone 3 | 10.20.3.0/25 | 10.20.3.1 | 10.20.3.2 – 10.20.3.126 | 126 |
| Site 2 / Zone 4 | Site 2 Zone 4 | 10.20.3.128/25 | 10.20.3.129 | 10.20.3.130 – 10.20.3.254 | 126 |
- Subnet
- 10.20.0.0/25
- Gateway
- 10.20.0.1
- DHCP
- 10.20.0.2 – 10.20.0.126
- Usable
- 126
- Subnet
- 10.20.0.128/25
- Gateway
- 10.20.0.129
- DHCP
- 10.20.0.130 – 10.20.0.254
- Usable
- 126
- Subnet
- 10.20.1.0/25
- Gateway
- 10.20.1.1
- DHCP
- 10.20.1.2 – 10.20.1.126
- Usable
- 126
- Subnet
- 10.20.1.128/25
- Gateway
- 10.20.1.129
- DHCP
- 10.20.1.130 – 10.20.1.254
- Usable
- 126
- Subnet
- 10.20.2.0/25
- Gateway
- 10.20.2.1
- DHCP
- 10.20.2.2 – 10.20.2.126
- Usable
- 126
- Subnet
- 10.20.2.128/25
- Gateway
- 10.20.2.129
- DHCP
- 10.20.2.130 – 10.20.2.254
- Usable
- 126
- Subnet
- 10.20.3.0/25
- Gateway
- 10.20.3.1
- DHCP
- 10.20.3.2 – 10.20.3.126
- Usable
- 126
- Subnet
- 10.20.3.128/25
- Gateway
- 10.20.3.129
- DHCP
- 10.20.3.130 – 10.20.3.254
- Usable
- 126
DNS / NTP / option reminders
- Set DNS servers, search/domain suffix, and NTP/time sources before production cutover.
- Voice networks may need DHCP option 66/150 or vendor-specific options; PXE may need boot options.
- Document lease duration, reservations, exclusions, and relay/helper addresses per VLAN.
Implementation checklist
- Run an overlap check against existing LANs, VPN pools, cloud VPC/VNET ranges, and partner/client networks.
- Assign an owner, purpose, security zone, and firewall policy expectation to every site/zone subnet.
- Reserve gateway, network infrastructure, static devices, and DHCP exclusions before enabling leases.
- Document DNS, NTP, DHCP options, relay/helper addresses, and lease durations per site or zone.
- Leave spare child subnets in the parent range for future sites, zones, or migrations.
- Spot-check high-growth zones against one larger subnet size.
Watch-outs
- Do not deploy overlapping ranges across sites, VPNs, cloud VPCs/VNETs, or client networks.
- Keep VLAN numbering consistent by site/zone, but adapt it to existing standards if they already exist.
- Reserve room for management, wireless, voice, camera, server, and guest networks separately where possible.
Planning notes
Use this as a worksheet and sanity check, not an automatic production configuration. Confirm VLAN IDs, routed interfaces, DHCP reservations, firewall rules, switch trunks, cloud ranges, and documentation standards before deploying changes.
Get a better answer from the Network Planner
- Start with the example values to see how the tool behaves.
- Swap in your own numbers, even if they are rough first-pass estimates.
- Change one input at a time so you can see what actually moves the result.
What the result means
The result turns network notation into something easier to read: ranges, host counts, masks, wildcard masks, ports, or planning blocks.
How to use it
Use the output to plan or double-check, then compare it with the real network before changing a route, VLAN, DHCP scope, firewall rule, or ACL.
What can change it
A valid network number can still be wrong for your environment if it overlaps, conflicts with routing, exposes traffic, or breaks change-control rules.
Good for
Plan multiple sites or buildings.
Check next
Compare your result with IP Overlap / VPN Range Checker, VLAN Planner, DHCP Scope Planner when you want more context.
Best habit
Run a conservative case and an optimistic case. The gap between them is often more useful than a single answer.
Common uses
- Plan multiple sites or buildings.
- Split zones like staff, guest, voice, and cameras.
- Estimate subnet sizes before implementation.
Common questions
Is the Network Planner private?
Yes. CalcShelf calculators run without an account, do not save calculator entries, and do not put raw inputs into shareable URLs or analytics events.
How accurate is the Network Planner?
It follows common IPv4, CIDR, mask, range, and port conventions. Production networks still need live-config, routing, ACL, overlap, and change-control review.
What should I check after using the Network Planner?
Verify live allocations, overlaps, gateway conventions, routes, ACL/firewall order, documentation, and rollback plan before production changes.
Which calculator should I try next?
Use the related calculators below to cross-check the same decision from another angle before you act.
Method behind the estimate
Networking tools use IPv4, CIDR, subnet mask, wildcard mask, range, VLAN, DHCP, and port-reference rules for planning and sanity checks.
Why the detail matters
Before changing production routing, firewall, VLAN, DHCP, or address plans, verify against the actual network, documentation, and change-control process.
Privacy guardrail
Your calculator values are for you. CalcShelf does not require an account, save calculator entries, put your numbers into shareable URLs, or use raw inputs as analytics events.
Copy or print safely
Use any copy, print, or worksheet controls as local handoff tools for your own notes, supplier calls, lender questions, or implementation checklist. They are there to help you explain the result to a human.
Before acting
Treat the result as a decision draft, not a verdict. Recheck the source numbers, run a downside case, and verify the real-world rule, quote, label, or spec that controls the final answer.
Last reviewed: May 11, 2026. See methodology and editorial policy for formulas, assumptions, rounding, review approach, and limitations. For network changes, verify against live configuration, vendor docs, and change-control requirements.