Cisco Switching: Top 10 Questions on StackWise Virtual Technology

Today I am going to talk about the questions on Cisco StackWise Virtual as there are lot of questions coming around. This article is based on the inputs asked by many users. Below are the basic questions and answers around Cisco StackWise Virtual, we will come up with other as well.

Source: Cisco Systems
Fig 1.1- StackWise Virtual
What is StackWise Virtual technology?
Cisco StackWise Virtual technology is next-generation and evolutionary StackWise technology. It enables unified system virtualization by expanding highly proven and industry-leading Cisco StackWise technology for mission-critical enterprise networks.

What is the difference between StackWise-480 and StackWise Virtual?
The existing StackWise technology significantly streamlines the access or distribution layer using high-speed back-panel StackWise ports and cables. The new StackWise Virtual increases switch stack function over the network ports and cables. This solution offers new design potential to virtualize networking devices much beyond a single rack unit space.

What are the benefits of new StackWise Virtual technology?
The next-generation distributed stacking mode brings common benefits of stacking at the network level instead of the individual system level:

Simple: Virtualize two redundant Cisco Catalyst switches as single logical entity in network topologies and from an operation perspective.
Reliable: Builds a unified control plane with Stateful Switchover (SSO) technology for nonstop business communication.
Scalable: Fully distributed forwarding architecture increases overall network bandwidth, resulting in improved user experience.
Manageable: Single management plane to operate as a single entity and integrated with Cisco APIC-EM and Cisco Prime Infrastructure management applications.

What is the StackWise Virtual Link (SVL)?
The SVL is a special inter chassis system link between two stack members in a StackWise Virtual domain. It enables extending stack fabric communication over network ports to virtualize the system. The SVL connections do not run any network protocol and remain transparent in Layer 2 and Layer 3 network topologies.

How does StackWise Virtual support high- availability mechanisms?
StackWise Virtual supports a 1+1 HA redundancy model using Cisco SSO and Nonstop Forwarding (NSF) technologies.

Which StackWise Virtual node handles all control and management plane protocols?
The stack member with SSO active in the current role centrally manages all network control and management plane protocols. The Layer 2 and Layer 3 protocol states are synchronized with the HOT_STANDBY stack member switch.

How does StackWise Virtual synchronize the forwarding plane between both stack members in a domain?
The SSO active switch builds Layer 2 and Layer 3 forwarding topologies based on various protocols. The SSO active programs local and peer stack member switch hardware to enable the distributed forwarding plane in the StackWise Virtual domain.

How does new StackWise Virtual technology compare to Cisco 6K/4K VSS technology?
The initial phase of StackWise Virtual capabilities offers consistent capabilities as a Cisco Catalyst 6K/4K VSS solution. However, the StackWise Virtual technology is a new innovation that is extended based on traditional stacking technology. It enables several new network design potentials, and with a combination of Cisco UADP ASIC technology and the next-generation Cisco IOS-XE Software operating system, it enables several new advanced technologies such as programmability, application visibility, Multiprotocol Label Switching (MPLS), and much more.

What is the SVL communication mechanism for both stack member switches?
All inter chassis system control communication between stack members is encapsulated over a special 64-byte StackWise Virtual Header (SVH). This communication is carried over reserved VLAN ID 4094 from the global range.

How does the dual active detection and recovery mechanism work?
The dual active fast hello is a lightweight protocol that operates on a dedicated interface between two stack member switches of a StackWise Virtual domain. If the SSO active switch receives a fast hello message after losing all SVL connections, it detects dual active failure and enters recovery-mode by disabling all network connection ports to minimize disruption.