Do you know about Cisco StackWise Virtual in Cisco Catalyst 9000 ?

Cisco Stackwise Virtual for the core switch is one of the important way of doing high availability, scalability in the switched network. Lets talk about the same in detail with the basics of Cisco Stackwise virtual with the configuration example.

Cisco StackWise Virtual consists of two switches into a single logical switch domain and operate as one switch with a large number of ports, offering a single point of management. One of the member switches is the control and management plane master, while the other one is the standby.

Fig 1.1- Cisco Stackwise Virtual

The virtualization of multiple physical switches into a single logical switch is only from a control and management perspective. Because of the control plane being common, it may look like a single logical entity to peer switches.

The data plane of the switches are converged, that is, the forwarding context of a switch might be passed to the other member switch for further processing when traffic is forwarded across the switches. An election mechanism that determines which switch has Cisco StackWise Virtual active and which one is a control plane standby, is available. 

The active switch is responsible for management, bridging and routing protocols, and software data path. These are centralized on the active switch supervisor of the Cisco StackWise Virtual active switch. 

Switch Status showing Stacking
NDNA-CAT9K #show switch
Switch/Stack Mac Address: 2eaf.be84.0a18 - Local Mac Address
Mac persistence wait time: Indefinite

Switch#          Role                  Mac Address              Priority              Current State
1                     Standby            2eaf.be84.0a18           10                        Ready
2                     Active               00b0.e1f2.6820           1                         Ready

Things to Remember:
StackWise Virtual : two Switches with single logical control plane

What is the difference between StackWise-480 and StackWise Virtual? 
The existing StackWise technology greatly simplifies the access or distribution layer using high-speed back-panel StackWise ports and cables. The new StackWise Virtual extends 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. 

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

What is the StackWise Virtual Link (SVL)? 
A The SVL is a special interchassis 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. 

What is the SVL communication mechanism for both stack member switches? 
All interchassis 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. 

Configuring Cisco StackWise Virtual
NDNA-CAT9K> enable 
NDNA-CAT9K# configure terminal 
NDNA-CAT9K(config)# stackwise-virtual 
NDNA-CAT9K(config-stackwise-virtual)# domain 2

Cisco StackWise Virtual Link
NDNA-CAT9K> enable 
NDNA-CAT9K# configure terminal 
NDNA-CAT9K(config)#interface TenGigabitEthernet1/1/3 
NDNA-CAT9K(config-if)#stackwise-virtual link 1 

StackWise Virtual Dual-Active-Detection link 
NDNA-CAT9K> enable 
NDNA-CAT9K# configure terminal 
NDNA-CAT9K(config)#interface TenGigabitEthernet1/1/3 
NDNA-CAT9K(config-if)#stackwise-virtual dual-active-detection