Conditions Virtual StackWise transmit data over virtual link?

[CiscoPurpleBelt]

Need some clarification on the Cisco doc which states:

CiscoStackWise Virtual transmits data traffic over aStackWise Virtual link under the following circumstances: • Layer 2 traffic flooded over a VLAN (even for dual-homed links).

• Packets processed by software on the Cisco StackWise Virtual active switch where the ingress interface is on the Cisco StackWise Virtual standby switch.

Does this mean that it uses the VL when packets are processed on the ingress interface of the stanby switch or the active switch?

[Reza Sharifi]

If I understand it correctly, it is on the ingress interface of the standby switch.

HTH

[Remi Astruc · Accepted solution]

Hello,

In a Stackwise Virtual pair, there is always one active and one standby switch.

In most of cases, unless specific traffic pattern, incoming packets are switched or routed in hardware, meaning at wire-speed on the switch receiving the packet (incoming switch).

But there are some cases where the incoming switch needs to perform a processing in CPU to handle the received packet (ACL logging, unknown destination, BPDU, etc...). That's precisely what the active switch is responsible for because it runs the processes and protocols in CPU, not the standby.

For that reason, when a packet incomes in the standby switch and needs to be pushed to a CPU process, it must cross the VL to the active switch.

Remi