Introduction to VPC and VSS
Both VPC and VSS are used basically to support multi-chassis ether-channel that means we can create a port-channel whose one end is device A, however, another end is physically connected to 2 different physical switches which logically appears to be one switch.
The Differentiation between both the feature set is tabled below –
|1||Feature specific to Nexus||Feature specific to catalyst 6500,4500 Series|
|2||Separate control plane for both switches.||2 Switches merge to form 1 logical Switch with a single control plane.|
|3||Separate IP for each switch management and configuration.||Single IP for management and configuration of 1 Logical Unit (2 Physical Chassis)|
|4||HSRP is required.||First Hop Redundancy Protocol like HSRP not required.|
|5||Separate instance of STP, FHRP, IGP, BGP etc. will be required on each physical Switch of VPC.||Same instance of STP, FHRP, IGP, BGP etc. will be used on each physical Switch of VSS.|
|6||Both the switches are active and work individually. Only from VPC perspective are they elected primary and secondary.||Switches are always primary and secondary from all aspects.|
|7||Supports L2 Port Channels||Supports L3 Port Channels|
|8||Supports LACP||Supports PAGP and LACP|
|9||Control messages are carried by CFS over Peer Link and a Peer keep alive link is used to check heartbeats and detect dual-active condition||Control messages and Data frames flow between active and standby via VSL|
Download the comparison table here.