Lab builder

The Lab builder creates a ready-to-use lab in GNS3: nodes, cabling, zone drawings, generated configs and full NetSimLab documentation, in one go.

Before you start

A GNS3 server at version 2.2.x or 3.1.0+, connected on its page (see Connect a GNS3 server).
GNS3 templates for the images the lab type uses (for example IOSv, IOSvL2 and VPCS for the campus lab).
The operator role to build. Anyone can plan and preview a lab.

1 · Lab type & server

Pick the Lab type and the GNS3 server:

Lab type	What it builds
Enterprise campus (3-tier)	An EDGE router doing NAT, an optional firewall (Palo Alto, FortiGate, ASAv, vSRX or pfSense), 2 core routers in OSPF area 0, 2 distribution switches with HSRP and an LACP trunk, access switches with user and voice PCs, and optional Datacenter and DMZ zones.
VXLAN BGP EVPN fabric (spine / leaf)	Nexus 9000v spines and leaves with an OSPF underlay, iBGP EVPN overlay (spines as route reflectors), multicast or ingress replication, a tenant VRF and servers to test layer-2 and layer-3 VXLAN.

2 · Parameters

Set the lab’s size and addressing. The preview on the right updates as you go:

Topology: the diagram, with zones.
Devices: every node, its role and resources.
IP plan: VLANs, subnets and gateways.
Configs: the generated config for each device.
Design notes: how the lab is put together and what to test.

The vCPU and RAM estimate warns you if the lab won’t fit on the server.

Enterprise campus options

Lab / GNS3 project name, Access switches and PCs per access switch.
Campus VLANs (up to 5): each with your own number and name (defaults: 10 USERS, 20 VOICE, 30 WIRELESS, 40 PRINTERS, 60 GUEST). Clear a VLAN’s number to use fewer.
Management VLAN number and name, Trunk native VLAN, DMZ VLAN number and name, and Datacenter VLAN number and name. Every VLAN number and name in the lab must be unique.
Firewall (or None, which connects EDGE straight to both cores), DMZ zone (switch + server) and Datacenter zone (L3 switch + server).
Build level, for practice labs where you build part of the network yourself:

Build level	Configured and cabled	Placed but left unconfigured and uncabled
Full lab	everything	nothing
Core + distribution	edge, firewall, core, distribution, datacenter	access switches, PCs, DMZ
Core	edge, firewall, core	distribution, datacenter, access, DMZ
None	edge, firewall	core, distribution, datacenter, access, DMZ

Every device is still placed on the GNS3 canvas. The missing cabling shows as dashed To cable lines in the preview, and each unconfigured device keeps its intended config as a solution you can look at or push later.

Address pools (Point-to-point pool, Loopback pool, Campus VLAN supernet, Datacenter servers subnet, DMZ subnet), Domain name, Admin username, Admin password and Enable secret.

VXLAN fabric options

Nexus 9000v model (9500v modular or 9300v fixed), Spines, Leaves, Servers on leaves, Tenant VLANs (each becomes L2VNI 10000 + VLAN), tenant supernet, replication mode, VRF, ASN and address pools.
RAM per Nexus node (default 12 GB) and vCPUs per Nexus node (default 4). NX-OS needs this much: with less, OSPF and BGP fail to start. NetSimLab raises the node’s RAM at build time if the GNS3 template has less.

3 · GNS3 templates

Map each device type (router, switch, PC, firewall, Nexus switch…) to one of your GNS3 templates. The best matches are pre-selected; check them.

4 · Build

Choose what happens after the nodes are created:

Start all nodes after building.
Push generated configs once devices have booted, with the Push method: Direct console (default; works on GNS3 2.2 and 3.1) or GNS3 MCP (3.1+ only).
Start-up order: a staged rollout (routers first, then switches one at a time, then PCs) is the default and the gentlest on the GNS3 server. All at once is faster if the server has plenty of RAM and CPU.
Pause between switches (seconds) and Attempts per device (a failed push is retried).
Wait before first login (minutes) — Nexus only, default 10. Nexus 9000v interfaces only come up about 10 minutes after boot, so NetSimLab answers the first-boot questions as they appear but waits this long before logging in.

Click Build “” in GNS3. Build progress shows each step and each device as it’s configured. When it’s done, click Open project in NetSimLab to see the documented lab, or Build another.

After the build

Enterprise campus: the EDGE router’s Gi0/0 is left uncabled. Connect it to a GNS3 NAT or Cloud node yourself for internet access; it’s already set up for DHCP and NAT.
VXLAN fabric: SRV1 and SRV2 start in the same VLAN (layer-2 VXLAN test). Move one to the other tenant VLAN to test layer-3 routing.
Firewall configs are generated for reference only and are not pushed.
To re-apply configs later, use Push planned configs on the project’s Devices & images tab (see Push configs to devices).