VSS Flashcards
What is VSS?
Virtual switching system. A high-availability redundancy protocol. A single IP address is shared between an active and a standby switch.
What does a VSS pair consist of?
An active and a standby switch.
What is the VSS active switch responsible for?
The full workload for the device. It handles all switching, routing and processing.
What is the VSS standby switch responsible for?
Taking over when the active switch goes down. The standby switch does not handle any of the workload besides MultiChassis Etherchannels.
What is a VSL?
Virtual switch link. It’s the link that the standby and active switch use to communicate. The VSL is also an etherchannel.
What is a MultiChassis Etherchannel?
An etherchannel consisting of bundled ports on both the active and the standby switch.
What two pieces of VSS create the super-fast redundancy?
SSO (stateful switchover) and NSF (non-stop forwarding)
How do you enable SSO and NSF?
They are enabled by default when VSS is configured.
How does the standby switch detect if the active switch has gone down?
Via the VSL.
If the active switch has gone down and the standby switch has taken over as the “new” active switch, what will happen to the “old” active switch when it recovers?
It will not resume the active switch role. Instead, it will become the “new” standby switch.
What is a dual-active situation, and what causes it?
A dual-active situation occurs when both switches in the VSS pair take on the active role, and is commonly caused by the VSL link breaking.
What is dual-active recovery?
Dual-active recovery is how VSS recovers from a dual-active situation (duh). The original active switch will put each of its non-VSL ports into err-disabled mode until the VSL has been repaired. Then, it will take on the standby role.
According to Cisco, what is VSS meant to replace?
First hop redundancy protocols (VRRP, GLBP, HSRP, etc.)
