VSS (Virtual Switching System) is a method to combine two physical switches into one logical switch to achieve physical redundancy, Spanning-Tree blocking elimination, and increased bandwidth. VSS was first available in Cisco 6500. And now it’s also supported on 4500 switches. In a VSS, the data plane of both clustered switches is active at the same time in both chassis. VSS members are connected by virtual switch links (VSLs) using standard Gigabit or 10 Gigabit Ethernet connections between the VSS members. VSLs can carry regular user traffic in addition to the control plane communication between the VSS members.
Although VSS can enable on Catalyst 4500/4500X series switch (Supervisor Engine7-E, Supervisor Engine 7L-E, and Catalyst 4500-X, and VSS is not supported on the Sup8), the following software, hardware and licensing requirement for Cisco 4500 VSS must meet.
4500-X–IP base or higher. (not supported in LAN base)
Sup7E–IP base or higher. (not supported in LAN base)
IOS-XE3.4.0SG/ 15.1(2) SG Software Release.
Linecard and port-type supported for VSL:
Sup7-E and Sup 7L-E Uplink Ports.
WS-X4748-RJ45V+E Speed: 1G
WS-X4712-SFP+E Speed: 10G
WS-X4748-UPOE+E Speed: 1G
WS-X4748-RJ45-E Speed: 1G
WS-X4606-X2-E Speed: Speed: 10G
WS-X4648-RJ45V-E Speed: 1G
WS-X4648-RJ45V+E Speed: 1G
WS-X4648-RJ45-E Speed: 1G
WS-X4640-CSFP-E Speed: 1G
WS-X4624-SFP-E Speed: 1G
WS-X4612-SFP-E Speed: 1G
45xx and lower Linecards:
Note: VSS on Sup8E is currently not supported-We have road map to support from IOS-XE 3.6., but will be added in a future release.
Reference from https://supportforums.cisco.com/document/12176526/software-hardware-and-licensing-requirement-4500-vss