Looking to indulge in network simulation? Or just need to set up a virtualization environment which also functions as a visual network diagram? You should try the open-source network simulation tool GNS3.
All you need is to provision a virtual machine, I would suggest using VMWare ESXI, HyperV, or Proxmox, as you will want enterprise virtualization features like KVM support and a type 1 hypervisor for better performance.
Download and Install
GNS3 VM Setup Instructions
https://docs.gns3.com/docs/getting-started/setup-wizard-gns3-vm
Downloading the GNS3 VM | GNS3 Documentation
Instructions for Hyper-V
You will need to download the two hard disks for the gns3 VM and attach them to your Hyper-V VM. The installation is similar to the setup on VMware ESXI Install the GNS3 VM on ESXi | GNS3 Documentation
If you want to connect your topology to your local network and allow your edge router to receive an IP address through DHCP, you will need to enable MAC address spoofing on your External V-Switch in Hyper-V (Image below). Or else the DHCP broadcasts will be blocked.
You will then need to enable nested virtualization for the VM. You can do this through PowerShell on the hypervisor machine.
Run Hyper-V in a Virtual Machine with Nested Virtualization | Microsoft Learn
See image below for my example configuration.
You can then download the client software to view and edit topologies on your desktop. Software | GNS3
Configuration
Configure a username and password for your gns3 server VM, you may also want to configure the network connections on the VM.
I configured an interface to have internet access using NAT on eth0 which is configured with dhcp, and I will be configuring the server on eth1 which is connected to a VSwitch only giving access to a dedicated client for the gns3 client software.
Now you should have a working GNS3 environment, just find network and end device images then you can start simulating networks.
Goals
I am planning on using GNS3 to study for the CCNA, and CCNP certifications. Here’s some of the main concepts I plan to study using GNS3 simulations.
1. Routing & Switching Foundations (CCNA‑level)
These are the bread‑and‑butter labs that Cisco expects you to master.
Build labs around:
- VLANs, trunking, DTP
- STP, RSTP, MSTP
- EtherChannel (L2/L3)
- Inter‑VLAN routing
- OSPF single‑area + multi‑area
- EIGRP basics
- HSRP/VRRP/GLBP
- DHCP, NAT, ACLs
Verified sources:
- Cisco’s official CCNA Prep CML labs
- Community CML topologies on GitHub
2. Data Center Switching (CCNP DC‑level)
These are the simulations that matter most for the DCICN/DCICT and DCCOR exam domains.
Build labs around:
- vPC (Virtual Port Channel)
- FabricPath (if images available)
- VXLAN EVPN (modern DC fabrics)
- Leaf‑Spine architectures
- Multicast in the data center
- FHRP in a DC environment
- L2/L3 boundary design
- OSPF/BGP underlay for VXLAN
Why these matter
They reflect real‑world Cisco ACI and NX‑OS design principles, even if you’re not running full ACI in CML.
3. NX‑OS Core Labs (CCNP Data Center)
If you have NX‑OS images in CML, build labs around:
- vPC peer‑link and keepalive
- Fabric Extenders (FEX)
- Port‑channels and LACP hashing
- VRF‑Lite segmentation
- OSPF/BGP on NX‑OS
- Static routing + redistribution
- SPAN/RSPAN/ERSPAN
These are directly aligned with CCNP DC blueprint topics.
4. Data Center Network Services
These are often overlooked but show up on the exam:
- DHCP relay in a DC
- NTP hierarchy
- Syslog + SNMP monitoring
- AAA (TACACS+/RADIUS)
- IPsec tunnels (site‑to‑site)
Verified source:
- Cisco Modeling Labs sample labs include IPsec exploration and AAA/TACACS examples.
5. Automation & Programmability (CCNA + CCNP DC)
Cisco is pushing automation.
Build labs that include:
- NETCONF/RESTCONF on IOS XE
- NX‑API on NX‑OS
- Python scripts to pull interface status
- Model‑driven telemetry basics
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