VLAN management
Add VLANs with an 802.1Q ID, name, purpose and description. Reserved and well known IDs, such as VLAN 1, the legacy Cisco range 1002 to 1005 and VLAN 4095, are flagged so they are not used by mistake.
VLAN, Subnet, and IP Address Planner
Plan IPv4 VLANs, VRFs, subnets, devices and interfaces in one place, catch address conflicts before deployment, and generate starter configuration for Cisco IOS and Arista EOS.
Included in the 14-day Pro trial on every new account. No credit card.
Walkthrough
See it working
Step 01
Start a project or load the example
Start a new project, open a saved one, or load the example schema to see a worked design. Projects save in the browser and to your account, and can be exported to JSON and imported again.
Step 04
Use VRFs for overlapping address space
Tag subnets with a VRF so the same range can exist in separate VRFs without false warnings. Duplicate address, overlap and DHCP checks all respect VRF boundaries.
Step 06
Bundle interfaces into port channels
Group interfaces into LACP or static port channels with a trunk, access or routed mode. The member interfaces take their settings from the bundle.
Step 09
Generate starter configuration
Choose Cisco IOS and IOS XE, Arista EOS or generic pseudocode and generate interface configuration for one device or all of them. Copy or download the output and review it before use.
Step 10
Export the schema
Export the full design to JSON for backup and reloading, or to CSV for spreadsheets, CMDB and IPAM tools.
Overview
Plan VLANs, subnets and IP address allocation
Every new site, refresh or network merger starts with the same work: define the VLANs, plan the subnets, list the devices, assign addresses and prepare the configuration. Mistakes made at this stage often stay hidden until later, such as a duplicate address that only matters when both devices are online, a static address inside a DHCP pool, or a trunk whose two ends disagree on the native VLAN.
Read the full overview
The VLAN, Subnet, and IP Address Planner keeps that work in one structured workspace. You define VLANs, plan subnets with their gateways, DHCP pools, reserved addresses and VRFs, and record each device with its interfaces, modes, VLANs, addresses and trunk peers. An address space view shows the free blocks in a site range and finds the next free subnet of a given size, and a VLSM split divides a subnet into equal parts.
Checks run as the design grows. The planner flags reserved VLAN IDs, duplicate addresses within a VRF, subnet overlaps, static addresses inside DHCP pools, duplicate port names and trunk mismatches. When the plan is ready it produces vendor style interface configuration as a starting point, and the whole schema exports to JSON or CSV.
Capabilities 8
Subnet planning
Each subnet carries its network and prefix, gateway, DHCP pool, reserved addresses, VLAN, VRF and description. The planner calculates the usable range, host count and utilisation, and checks that the gateway, pool and reservations sit inside the subnet.
VRF aware checks
Subnets can be tagged with a VRF, and duplicate address, overlap and DHCP checks respect those boundaries. The same address range can exist in two VRFs without false warnings, while true overlaps within a VRF are still flagged.
Devices, interfaces and port channels
Record switches, routers, firewalls, servers and endpoints with their interfaces. Each interface can be access, trunk, routed, loopback or management, with VLANs, voice VLAN, address and DNS name, and interfaces can be bundled into LACP port channels.
Trunk peer checks
Document the far end of a trunk and the planner checks both ends for native VLAN and allowed VLAN agreement, and for a trunk that lands on a non-trunk port. It also warns about undefined VLANs on a trunk and a native VLAN of 1.
Address space and VLSM
Map the allocations inside a site block for a chosen VRF, see the free space as CIDR blocks, and find the next free subnet of a chosen size. A VLSM split divides an existing subnet into equal child subnets.
Starter configuration
Generate interface configuration for each device in Cisco IOS and IOS XE, Arista EOS or generic pseudocode, covering VLANs, VRFs, port channels, interface modes and addresses. The output is a planning starting point, not a complete device configuration, and should be reviewed before use.
Export and saved projects
Export the full schema to JSON for backup and reloading, or to CSV for spreadsheets, CMDB and IPAM tools. Projects save in the browser and to your account.
Inputs and outputs
What goes in, what comes out
Inputs 11
- VLAN ID, name, purpose and description
- Subnet network and prefix (IPv4 CIDR)
- Gateway, DHCP pool and reserved addresses for each subnet
- VLAN and VRF for each subnet
- Devices with name, type and location
- Interface mode, VLANs, voice VLAN and port name
- Interface address, DNS name and subnet
- Trunk peer device and port
- Port channel members and LACP mode
- Analysis block and VRF for the address space view
- Configuration target: Cisco IOS and IOS XE, Arista EOS or generic
Outputs 11
- VLAN list with reserved ID flags
- Subnet table with usable range, host count and utilisation
- Free address blocks and the next free subnet of a chosen size
- Device, interface and port channel inventory
- IP schema grouped by subnet, with DNS names and search
- Duplicate address and subnet overlap warnings within each VRF
- Static address in DHCP pool warnings
- Duplicate port name and trunk mismatch warnings
- Vendor style starter configuration to copy or download
- JSON export of the full schema
- CSV export of the schema
Standards & methodology
- IEEE 802.1Q VLAN tagging and reserved VLAN IDs
- RFC 1918 private IPv4 address space
- RFC 6598 shared address space (CGNAT)
Use cases
When to use this tool
- 01Designing the IP schema for a new site, campus or data centre
- 02Managing VLAN IDs and avoiding reserved ranges
- 03Planning subnets, DHCP scopes and reserved addresses together
- 04Modelling overlapping address space with VRFs
- 05Documenting devices, interfaces, trunks and port channels
- 06Finding address conflicts and static addresses inside DHCP pools
- 07Finding the next free subnet within a site block
- 08Generating starter interface configuration for new switches
Does it cover IPv6?
No. The planner works with IPv4 and CIDR prefixes, which is where most VLAN, subnet and DHCP planning on enterprise and industrial networks still happens.
Why does it warn me about VLAN 1, 1002 to 1005 and 4095?
These IDs are reserved or well known and are best kept away from general traffic. VLAN 1 is the default VLAN on many switches and a common VLAN hopping vector when used as a native VLAN. VLANs 1002 to 1005 are reserved for legacy FDDI and Token Ring on Cisco IOS, and VLAN 4095 is reserved by 802.1Q.
How does VRF scoping work?
Each subnet can carry a VRF label. Duplicate address, subnet overlap and DHCP checks only compare subnets in the same VRF, so overlapping ranges in separate VRFs, such as separate tenants or IT and OT networks, do not raise false warnings.
What conflicts does it detect?
It flags duplicate addresses within a VRF, subnets that overlap within a VRF, static addresses inside a DHCP pool, duplicate port names on a device, and trunk mismatches on native VLAN or allowed VLANs. Each warning links to the entry that needs attention.
What does the configuration output cover?
It produces interface level configuration for each device in Cisco IOS and IOS XE, Arista EOS or generic pseudocode, including VLANs, VRFs, port channels, interface modes and addresses. It does not cover AAA, routing protocols, ACLs, first hop redundancy, QoS or other global settings, and it should be reviewed before it is applied to a device.
Can it tell me where the next free subnet fits?
Yes. Enter a site block and a VRF, or let the planner find the smallest block covering that VRF, and it maps the existing allocations and lists the free space. It can also name the first free subnet of a chosen prefix length and add it to the plan.
Where is my design stored?
Projects are saved in your browser and to your account, so they are kept between sessions. You can also export the design to JSON as a backup or to share it, and import it again later.
Free for 14 days
Included in the 14-day Pro trial on every new account. No credit card.