Posts tagged: #troubleshooting
GNS3 alternatives compared as of October 2026: EVE-NG, Containerlab, Cisco CML, Kathará, netlab and Isothrum. Licensing, what they run, and who each fits.
The GNS3 app runs on M-series Macs, but the x86 GNS3 VM doesn't. What the ARM64 VM can run, its limits, and when to use a remote server.
GNS3 appliance stuck on Missing files or This is not the correct file? Match the MD5, put the image where the wizard looks, and finish the import.
GNS3 can't reach the server inside the GNS3 VM. Find the VM's IP, test port 3080, fix the host-only network, versions and firewall.
GNS3 console won't open or telnet shows nothing? Start the node, fix the console command, install a telnet client and check the console host and port.
A GNS3 Docker node can't reach the internet or resolve names. Link it to a NAT node, enable DHCP in /etc/network/interfaces, check DNS and forwarding.
Each Dynamips router pins a CPU core until it has a working Idle-PC value. Compute one with Idle-PC or Auto Idle-PC and check the CPU drops.
The GNS3 VM can't see VT-x or AMD-V. Enable nested virtualization in BIOS, Windows and your hypervisor, then check it with kvm-ok.
GNS3 needs one free host-only VMnet per adapter of a VMware VM. Create them from Preferences or the Virtual Network Editor, then start the node.
GNS3 refuses to connect when the app, the GNS3 VM or a remote server run different versions. Find each version, then upgrade so all match.
GNS3 VM won't start, consoles won't open, captures stay empty? Find your error and the fix, from KVM and VMnet to uBridge, Wireshark and Dynamips.
Docker or NAT nodes won't start on Linux because uBridge lacks network capabilities. Reconfigure the package, set the capabilities, re-login.
Dynamips couldn't open the UDP port for a link. Find what holds the port, move GNS3's UDP tunneling port range, and start the project again.
VT-x/AMD-V errors for the GNS3 VM on Windows come from Hyper-V, Memory integrity or the BIOS. Find which one holds VT-x and free it.
GNS3 packet capture won't start, Wireshark errors out or shows no packets. Check the running node, the capture command, the Wireshark path and permissions.