VSS Flashcards
(34 cards)
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.)
What is the function of NSF?
provide nonstop forwarding in the event of failure of one of the member supervisors
Which statement describes what happens if all VSL connections between the virtual switch members are lost?
The VSS transitions to the dual active recovery mode, and only the new active virtual switch continues to forward traffic.
Which statement describes what happens when a switch enters dual active recovery mode?
All interfaces are shut down in the formerly active virtual switch member, but the new active virtual switch forwards traffic on all links.
Which option is a benefit of using VSS?
removes the need for a First Hop Redundancy Protocol
what does the RP do?
receives the first packet of a traffic flow and routes it
what does the SP do?
listens to the first packet going to router and away from the router. If it can switch in both directions, it learns a shortcut path so subsequent packets can be switched without the RP
When it comes to switch redundancy, what is NSF?
Non-Stop Forwarding. It is a method that focuses on rebuilding the Routing Information Base after a supervisor switch-over.
What are the fail-over times for the following redundancy modes: RPR, RPR+, SSO?
-RPR >2minutes-RPR+ >30seconds-SSO >1second
What routing protocols are supported by NSF?
-BGP, EIGRP, OSPF, IS-IS
What are the three redundancy modes used on Catalyst switches with more than one supervisor?
-RPR(Route Processor Redundancy ->Cold standby)-RPR+(Route Processor Redundancy+ ->Warm standby)-SSO(Stateful Switch Over ->Hot standby)
What does VSS stand for?
Virtual Switching System
