Running Multiple OcNOS VMs in GNS3: Lab Setup and Configuration Guide

GNS3 is one of the most popular network simulation platforms for building multi-vendor topologies. Its visual drag-and-drop interface and QEMU/KVM integration make it an ideal environment for running multiple OcNOS VM instances side by side — testing IS-IS adjacencies, BGP peering, MPLS label distribution, and EVPN services across a realistic multi-node topology before touching any hardware.

Prerequisites

• GNS3 installed (version 2.2+ recommended) with GNS3 VM for QEMU support
• OcNOS Demo VM downloaded from IP Infusion’s website (QEMU image format)
• Minimum 8GB RAM available for a 3-node topology (each OcNOS VM requires ~1.5–2GB)
• Linux or macOS host recommended; Windows requires GNS3 VM via VMware/VirtualBox

Importing OcNOS into GNS3

# Shell commands for GNS3 VM (Linux) -- prepare OcNOS QEMU image
#
# Step 1: Copy OcNOS QEMU image to GNS3 images directory
cp OcNOS-Demo-VM.qcow2 ~/GNS3/images/QEMU/

# Step 2: In GNS3 GUI -- Edit > Preferences > QEMU VMs > New
# Configure:
#   Name: OcNOS
#   QEMU binary: /usr/bin/qemu-system-x86_64
#   RAM: 1536 MB (minimum), 2048 MB recommended
#   HDA disk image: OcNOS-Demo-VM.qcow2
#   Network adapters: 8 (eth-0-0 through eth-0-7)
#   Console type: telnet

# Step 3: Verify OcNOS appliance appears in GNS3 device panel
# Drag OcNOS nodes into topology canvas and connect them

Sample 3-Node IS-IS SR Topology in GNS3

! OcNOS VM in GNS3 -- R1 IS-IS SR configuration
! (Apply same pattern to R2 and R3 with their own addresses/SIDs)
!
interface lo
  ip address 10.0.0.1/32
  ip router isis CORE
  isis segment-routing prefix-sid index 1
!
interface eth-0-1
  no shutdown
  ip address 192.168.12.1/30
  ip router isis CORE
  isis network point-to-point
  isis metric 10
!
router isis CORE
  net 49.0001.0000.0000.0001.00
  is-type level-2-only
  segment-routing mpls
  fast-reroute per-prefix level-2 ti-lfa
  !
  address-family ipv4 unicast
    segment-routing mpls
  exit-address-family
!
! Verify from R1:
show isis neighbor
show isis segment-routing prefix-sids
show mpls forwarding-table
! Ping R3 loopback via SR-MPLS:
ping mpls ipv4 10.0.0.3/32

Tips for Running Multiple OcNOS VMs in GNS3

• Use GNS3 VM — running OcNOS QEMU images requires KVM acceleration; the GNS3 VM on VMware ESXi or Workstation provides nested virtualization
• Snapshot frequently — save GNS3 snapshots after each major topology milestone so you can roll back without reconfiguring from scratch
• Console all nodes — use GNS3’s “Console all” feature to open terminal sessions to all OcNOS VMs simultaneously
• Disable unused interfaces — OcNOS VM boots with all interfaces up; shut down unused ones to reduce log noise

• OcNOS VM Overview
• EVE-NG Guide for OcNOS VM
• ContainerLab Guide for OcNOS VM
• Download OcNOS Demo VM

IP Infusion Product Team