Router> show version Cisco IOS Software, 3725 Software (C3725-ADVENTERPRISEK9-M), Version 12.4(15)T5 ROM: System Bootstrap, Version 12.4(13r)T5 Router uptime is 0 minutes System image file is "flash:c3725-adventerprisek9-mz.124-15.t5.bin"

C3725-adventerprisek9-mz.124-15.t5.bin Download May 2026

Note: This image supports MPLS but not MPLS VPN full (VRF-lite only). For full MPLS VPN, consider IOS 15.x or IOS XR.

In the GNS3 console, after starting the router: C3725-adventerprisek9-mz.124-15.t5.bin Download

Router> show version
Cisco IOS Software, 3725 Software (C3725-ADVENTERPRISEK9-M), Version 12.4(15)T5
ROM: System Bootstrap, Version 12.4(13r)T5
Router uptime is 0 minutes
System image file is "flash:c3725-adventerprisek9-mz.124-15.t5.bin"

Let’s break down the filename piece by piece. Understanding the nomenclature helps you know exactly what you are downloading. Note: This image supports MPLS but not MPLS

mz: Refers to the image format and compression (typically runs from RAM and is compressed).

124-15.t5: The IOS version. This is Cisco IOS version 12.4(15)T5. The 'T' stands for the Technology Train, meaning it includes newer features like advanced QoS, IPv6, and zone-based firewalls compared to mainline IOS.

.bin: The binary file extension—this is the executable IOS image.

In summary, this file is a feature-rich, encrypted IOS image for the Cisco 3725 router, running IOS version 12.4(15)T5. In the GNS3 console, after starting the router: