virtual switching system :VSS is a network systems virtualization technology that bundles multiple Cisco Catalyst 6500 Series switches into a single virtual switch, increasing operational efficiency, driving seamless communications, and scaling system bandwidth capacity to 1 .4Tbps. In the initial phase, a VSS will allow two physical Cisco Catalyst 6500 Series. The VSS is made up of the following:

• VSS Members: Cisco Catalyst 6500 Series Switches (up to two early release switches) deployed with Virtual Switching Supervisor 720 10GE
• Virtual Switch Link (VSL): 10 Gigabit Ethernet connections (up to eight with EtherChannel) between members.
• 10 Gigabit Ethernet connections must be one or more of the modules: Switching Supervisor 720 10GE: 10 Gigabit Ethernet uplink ports

VSS enables unprecedented campus network functionality and availability by integrating systems and network redundancy into a single node. It is the tested and certified Cisco Safe Harbor program. allows us

• Maximize network performance
• Increase network availability
• Simplify network architecture
• Reduce administrative burden
• virtualization support

Terminology:

• VSS1440:-

VSS1440 refers to the VSS consisting of two Cisco Catalyst 6500 Series switches with the 720-10GE Switching Supervisor. In a VSS, the data plane and switch fabric with 720 Gbps supervisor engine capacity in each chassis are active at the same time in both chassis, combining for 1400 Gbps active switching capacity per VSS. Only one of the virtual switch members has the active control plane. Both chassis are kept in sync with the inter-chassis Stateful Switchover (SSO) mechanism along with Nonstop Forwarding (NSF) to provide continuous communication even in the event of failure of one of the member supervisor engines.

• Stateful SwitchOver (SSO) mechanism:

A VSS uses inter-chassis NSF/SSO as the primary mechanism for high availability between the two chassis. One virtual switch member chassis will act as the active virtual switch member, while the other member will be in an active standby state for the control plane. Note that the data planes of both chassis are active and therefore forward traffic at a combined total capacity of 1440 Gbps. When one of the members of the virtual switch fails, there is no protocol reconvergence in the network. Access layer or core layer switches continue to forward the traffic because they only detect a link failure in an EtherChannel packet and therefore do not need to reconverge any protocols. There is no interruption to the traffic that flows through the VSS. The VSS mechanism during breaker failure is far superior compared to the traditional model where breaker failure results in indeterministic convergence of multiple control protocols like STP, HSRP, and routing protocol.

• Multi-Chassis Ether Channel (MEC):

Multi-Chassis EtherChannel (MEC) is a Layer 2 multipathing technology. This form of EtherChannel allows a connected node to terminate the EtherChannel through the two physical Cisco Catalyst 6500 Series switches that make up the VSS, leading to the creating a simplified loop-free Layer 2 topology. Using MEC in the VSS topology results in all links being up while providing a highly available topology without spanning tree protocol dependency. With the introduction of 12.2(33)SXI, the virtual switching system supports a maximum number of 512 MECs.

• Virtual Switch Link (VSL):

The connection used for communication between the two chassis. VSLs can be configured with up to eight links between the two switches on any combination of line cards or supervisor ports to provide a high level of redundancy. If for some strange reason all VSL connections between switch members are lost and both members are active, the VSS will go into dual active failback mode. The dual active state is detected quickly (subsecond) by any of the following three methods:

• PAgP enhancement used in MEC with the connection of Cisco switches
• Configuring L3 Bidirectional Forwarding Detection (BFD) on a directly connected link (in addition to VSL) between switch members or across an L2 link via an access layer switch
• Configuring Dual L2 Fast-Hello Active Detection on a directly connected link (in addition to VSL) between switch members (12.2(33)SXI compliant) In Dual Active Failover mode, all interfaces except VSL interfaces are in an operative closing state on the previously active switch member. The new active virtual switch continues to forward traffic on all links.

Need for VSS: The process of designing a fast and reliable network infrastructure is challenged by new business requirements. The need for seamless communication is becoming a basic starting point for most campus networks.

• High Bandwidth Environments
• Virtualization (VM)
• 10Gbps
• High availability environments
• Minimize network downtime
• redundant infrastructure
• Reduction in the number of devices to manage.

Deployment Areas for VSS:

• Campus core or data center/distribution layer
• Data center access (server connectivity)

VSS Benefits:

VSS offers superior benefits compared to traditional Layer 2/Layer 3 network design. The benefits can be grouped into the following categories:

• Reduce administrative burden: 1 active control plane = 1 logical switch. Using VSS there is a 50% reduction in the number of switches that need to be managed. The time to properly prepare for a change window can be drastically reduced. Approximately 60% of network failures are caused by human error.
• It reduces the number of times you and I have to touch the switch and we can reduce network failures
• Maximize network performance – double your bandwidth

2 active forwarding planes (720 Gbps each)

2 of 720 Gbps = 1440 Gbps (1.44 Tbps)

• Increase Network Availability: Multi-Chassis EtherChannel (MEC) allows us to reduce the number of neighbor adjacencies, eliminate SPF, DUAL and STP calculations in the event of a single link failure or VSS chassis failure.
• Perform IOS and chassis upgrades with minimal disruption.
• Only one gateway IP address per VLAN is required, instead of the three IP addresses per VLAN used.