Network Design
Unified IPv4 VLAN, VRF, subnet, device, and interface planner with VRF aware conflict detection, DHCP in static warnings, and vendor style configuration generation for Cisco IOS, IOS XE, and Arista EOS.
Every greenfield network deployment, every site refresh, and every M and A integration begins with the same workflow. Define the VLANs. Plan the subnets. List the devices. Assign addresses. Generate configuration. Validate before deployment. The work is not glamorous but doing it badly creates problems that take months to surface. A duplicated IP that only manifests when both endpoints are online. A subnet that overlaps quietly across two VRFs and breaks routing on the day the second VRF is enabled. A trunk port carrying a reserved VLAN that suddenly drops traffic when an upstream switch is upgraded. A static address inside a DHCP pool that conflicts with a lease six months later. Every one of these is preventable with a structured planning workspace.
The noIM₃ VLAN, Subnet, and IP Address Planner is that workspace. Five tabs walk through the design top to bottom. VLANs handles 802.1Q VLAN ID management with automatic flagging of reserved and well known IDs (VLAN 1 default, 1002 to 1005 FDDI and Token Ring legacy on Cisco IOS, 4095 reserved by 802.1Q). Subnets covers CIDR planning, gateway, DHCP pool start and end, reserved IPs with labels, VRF scoping, and per subnet utilisation with green, amber, and red banding. Devices captures switches, routers, and hosts with their interfaces, access, trunk, routed, loopback, or management mode, allowed VLAN lists, voice VLAN, port names, DNS hostnames, and trunk far end documentation. IP Schema presents every assigned address grouped by subnet with a DNS name column and search across IP, subnet, port, device name, and description. An Address Space card maps the free blocks inside any analysis block and finds the next free subnet of a chosen size.
Conflict detection runs throughout. VRF scoped duplicate IP detection so the same address space can legitimately exist in two VRFs without spurious warnings. Static in DHCP overlap detection so a fixed assignment never collides with a lease. Subnet overlap warnings within the same VRF that distinguish true overlap from simple containment. Duplicate port name detection per device. Trunk peer mismatch detection across documented links, covering native VLAN and allowed list agreement. Reserved VLAN ID flagging on every interface assignment. Every warning class surfaces in a clickable health strip that jumps straight to the offending tab and device. The Config tab generates vendor style interface stanzas per device for Cisco IOS and IOS XE, Arista EOS, or a generic pseudocode target, with a clear banner that the output is a planning starting point and does not cover AAA, NTP, banners, ACLs, FHRP, routing protocols, spanning tree global config, port security, storm control, or QoS. JSON export preserves the full schema for round trip editing. CSV export flattens the IP schema for CMDB and spreadsheet import.
Add VLANs with ID, name, and description. Reserved and well known IDs are flagged automatically. VLAN 1 as the default VLAN to avoid for user and trunk traffic. VLANs 1002 to 1005 as FDDI and Token Ring legacy reservations on Cisco IOS. VLAN 4095 as reserved by 802.1Q. Reserved VLANs render with a visible warning so the design never accidentally ships a booby trap.
Each subnet carries network and prefix, gateway, DHCP pool start and end, reserved IP list with labels, VLAN binding, VRF tag, and a description. Real time per subnet utilisation with colour coded banding (green below 60 per cent, amber below 85 per cent, red above). Overlap detection compares every subnet pair within the same VRF and warns on true overlaps that are not simple containment.
Every subnet can be tagged with a VRF label. Conflict detection, DHCP in static checks, and overlap warnings are all VRF scoped, so the same 10.0.0.0 slash 24 can legitimately exist in two different VRFs without raising spurious warnings. The reference panel surfaces the active VRF count at a glance.
Track switches, routers, and hosts with named interfaces. Each interface carries a mode (access, trunk, routed, loopback, or management), the assigned VLAN for access mode, an allowed VLAN list and native VLAN for trunk mode, an optional voice VLAN for IP phones, a port name, a DNS hostname, an IP address, a subnet binding, and a description. Rapid entry with Add plus next auto increments port names so a 48 port switch is documented in seconds. Duplicate port names on the same device are flagged. Per interface warnings surface static addresses that fall inside a DHCP pool.
Document the far end of any trunk by selecting the peer device and port — recording one end is enough, the link displays on both. The planner then checks the link for native VLAN disagreement, allowed VLAN list differences, and a trunk landing on a non trunk port, and flags any mismatch on the interface row and in the clickable health strip. This catches the classic VLAN hopping and dropped traffic misconfigurations on paper, before they ship to a switch.
Set an analysis block (for example 10.0.0.0/16) and a VRF, or let the planner auto detect the smallest covering supernet. An allocation bar maps every subnet at its true position, free space is decomposed into maximal CIDR blocks rendered as click to add chips, and a next free finder names the first available subnet of a chosen prefix length. This answers the planner question — where does the next /26 fit — directly from the schema.
The IP Schema tab presents every assigned address grouped by subnet, sorted numerically, with a DNS name column and search across IP, subnet, port, device name, and description. Gateway and DHCP pool context render in the header of each subnet block. Conflicts are computed VRF scoped across interface addresses and reserved IPs. Static addresses that land inside a DHCP pool are flagged as a separate warning class, and only problem rows carry badges so anything highlighted needs attention.
The Config tab emits interface stanzas per device for Cisco IOS and IOS XE, Arista EOS, or a generic pseudocode target. Output reflects access versus trunk mode, native VLAN, allowed VLAN lists, voice VLAN, IP addresses, and gateways. A prominent banner reminds the engineer that output is a planning starting point and does not cover AAA, NTP, banners, ACLs, FHRP (HSRP and VRRP), routing protocols (OSPF and BGP), spanning tree global config, port security, storm control, or QoS.
Export the full design to JSON for round trip editing. JSON preserves VLANs, subnets, devices, interfaces, VRF tags, and reserved IP lists so the design can be reloaded into the planner without loss. CSV export flattens the IP schema to a single sheet ready for review in spreadsheets, CMDBs, or IPAM tools.
Live counts for VLANs, subnets, devices, interfaces, active VRFs, reserved IPs, and static in DHCP overlaps. Quick reference for VLAN ID rules and access versus trunk behaviour. The panel updates as the schema evolves so design state is visible without leaving the workspace.
Runs entirely in your browser. No VLAN identifiers, subnet plans, device inventories, or IP assignments are submitted to a server. Useful for commercially confidential network design work, defence and intelligence networks, and environments where information security policy prohibits sending network plan data to third party services.
Reach for the VLAN, Subnet, and IP Address Planner in any of the following situations.
IPv4 with CIDR. IPv6 work is handled in the noIM₃ IP Network Designer and Capacity Planner, which covers VLSM allocation across IPv4 and IPv6 alongside link capacity and growth planning. Use this VLAN, Subnet, and IP Address Planner for the day to day VLAN, subnet, device, and IP schema design that an engineer maintains during deployment and operations.
These VLAN IDs are reserved or well known and should not be used for general user or trunk traffic. VLAN 1 is the Cisco default VLAN and is best avoided for production traffic because of how some platforms handle it on trunks. VLANs 1002 to 1005 are FDDI and Token Ring legacy reservations on Cisco IOS. VLAN 4095 is reserved by 802.1Q itself. Reserved VLANs render with a visible warning so the design never accidentally ships a configuration that hits one of these.
Every subnet can be tagged with a VRF label. Conflict detection (duplicate IP), DHCP in static checks, and subnet overlap warnings are all VRF scoped, so the same 10.0.0.0 slash 24 can legitimately exist in two different VRFs without raising spurious warnings. This matches the way real networks segregate overlapping address space (multi tenant, IT versus OT, customer separation) without renumbering.
Interface stanzas per device for Cisco IOS and IOS XE, Arista EOS, or a generic pseudocode target. Access versus trunk mode, native VLAN, allowed VLAN lists, voice VLAN, IP addresses, and gateways. A prominent banner on the output reminds the engineer that this is a planning starting point and does not cover AAA, NTP, banners, ACLs, FHRP (HSRP and VRRP), routing protocols (OSPF and BGP), spanning tree global config, port security, storm control, or QoS. Use the QoS and Traffic Classification Planner for the QoS configuration.
Five classes of warning are surfaced. VRF scoped duplicate IP detection across interface addresses and reserved IPs. Static in DHCP pool detection where an interface or reserved address falls inside a configured DHCP pool. Subnet overlap detection within the same VRF, distinguishing true overlap from simple containment. Duplicate port name detection per device. Trunk peer mismatch detection across documented links, covering native VLAN disagreement, allowed VLAN list differences, and a trunk landing on a non trunk port. Each warning renders as a clickable chip in the health strip that jumps straight to the offending tab and device, so remediation is direct rather than a search.
Yes. The Address Space card on the Subnets tab takes an analysis block (for example 10.0.0.0/16) and a VRF — or auto detects the smallest supernet covering the VRF — and maps every allocation on a proportional bar. Free space is decomposed into maximal CIDR blocks shown as click to add chips, and a next free finder names the first available subnet of a chosen prefix length, pre filling the Add Subnet form with one click. Subnets that contain the analysis block are treated as containers rather than allocations, so a declared site supernet does not mark the whole block used.
Yes. Each subnet has a reserved IP list with labels (for example printer pool, network management, monitoring servers, default gateway range) so the planner knows which addresses are off limits to DHCP and avoids accidental conflicts. Reserved IP utilisation feeds into the per subnet utilisation banding alongside assigned interface addresses.
JSON export preserves the full schema (VLANs, subnets, devices, interfaces, VRF tags, reserved IP lists) for round trip reloading into the planner. CSV export flattens the IP schema to one row per assigned address ready for spreadsheet review or CMDB import. Together they cover the formats network engineers actually use for documentation, backup, and integration with other tooling.
No. The planner runs entirely in your browser. No VLAN identifiers, subnet plans, device inventories, or IP assignments are submitted to a server. Useful for commercially confidential network design work, defence and intelligence networks, and environments where information security policy prohibits sending network plan data to third party services.
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