Virtual Switching System – VSS
What is a Virtual Switching System (VSS)?
- A VSS is network system virtualization technology that pools multiple Cisco Catalyst 6500 Series switches into one virtual switch.
- It helps in increasing operational efficiency, boosting nonstop communication & scaling system bandwidth capacity up to 1.4 Tbps
- We can manage 2 Cisco Catalyst 6509 chassis as a single 18 slot chassis once VSS is enabled.
- VSS eliminates spanning tree & provides increased bandwidth.
- Catalyst 6500 & Catalyst 4500 series
- Virtual Switching Supervisor 720-10GE (VS-S720-10GE-3C and VS-S720-10GE-3CXL) with IOS 12.2(33)SXH1 & IP Base
- Supervisor 2T (VS-S2T-10G and VS-S2T-10G-XL) with IOS 12.2(50) SY and IP Base
The peer switches which needs to form the VSS should be identical to each other with respect to both hardware & software version.
Cisco VSS – Logical Representation:
Cisco VSS Architecture:
- Virtual Switching System allows the combination of 2 switches into a single, logical network entity from the network control plane & management perspective.
- VSS uses Cisco IOS Stateful Switchover (SSO) & Non-Stop Forwarding (NSF) to provide a single logical switching & routing entity.
- To neighboring devices the VSS appears as a single logical switch.
- From data plane & traffic-forwarding perspective both switches in the Virtual Switching System actively forward traffic.
- From Control plane perspective one switch will be active & the other will be standby.
- 1 Active redundant control plane
- 1 Config
- Single point of management
- 2 active data planes
- Standby switch is essentially a set of additional line cards
- Control messages & Data frames flow between active and standby via VSL (can be seen as backplane extension)
- Special encapsulation on VSL frames to carry additional information
- VSL is a dedicated link which bonds the 2 chassis together into a single logical node.
- This link is responsible for transferring both data & control traffic between the peer chassis.
- The VSL is formed as a Cisco Ether Channel interface which carries VSS control traffic & normal data traffic.
- Up to 8 physical ports can form the ether channel for forming the VSL link.