Cisco Iou: L3 - Gns3

Breathing New Life into Old Labs: A Deep Dive into Cisco IOU L3 on GNS3

Here is everything you need to know about why IOU L3 still matters and how to make it sing in GNS3. Simply put, IOU (often called IOSv or L2/L3 IOU ) is an emulator that runs Cisco IOS directly as a Linux userspace process. Unlike traditional Dynamips (which emulates the CPU), IOU virtualizes the IOS environment. Cisco IOU L3 - GNS3

April 17, 2026 | Category: GNS3 Tutorials | Reading Time: 5 minutes Breathing New Life into Old Labs: A Deep

In GNS3, go to Edit > Preferences > QEMU & IOU > IOU Devices . Click New . April 17, 2026 | Category: GNS3 Tutorials |

Choose the ID (e.g., [L3] Cisco 7200 (IOU) ). Set the RAM to 512 MB (even 256 works, but 512 is safe).

IOU requires a license file called iourc . You must place a valid iourc file in the GNS3 config directory (usually ~/.GNS3/ on Linux/Mac or %LOCALAPPDATA%/GNS3 on Windows). A sample iourc entry looks like: [license] hostname = 12345678

GNS3 will ask for the path to your IOU binary (e.g., L3-ADVENTERPRISEK9-M-15.4-2T.bin ).