: Indicates the Cisco IOS Software Version. In this case, it is IOS Version 15.5(2)T . The "T" release train represents the Technology Train, which introduces new features, bug fixes, and hardware support before they are rolled into a Mainline release.
For those studying Service Provider architectures, this image supports core Multiprotocol Label Switching (MPLS) features: MPLS Layer 3 VPNs (L3VPN) LDP (Label Distribution Protocol) MPLS Traffic Engineering (TE) 3. Comprehensive IPv6 Support I86bi-linux-l3-adventerprisek9-ms.155-2.t.bin
These newer images offer better stability, 64-bit architecture support, and more recent feature implementations. : Indicates the Cisco IOS Software Version
Cisco IOL (), also called IOU (IOS on Unix), is a technology originally created by Cisco for internal software testing. It was later adopted by the networking community to power emulation platforms like GNS3 and EVE-NG. It was later adopted by the networking community