VSS

Question 1

What is VSS?

Answer 1

Virtual switching system. A high-availability redundancy protocol. A single IP address is shared between an active and a standby switch.

Question 2

What does a VSS pair consist of?

Answer 2

An active and a standby switch.

Question 3

What is the VSS active switch responsible for?

Answer 3

The full workload for the device. It handles all switching, routing and processing.

Question 4

What is the VSS standby switch responsible for?

Answer 4

Taking over when the active switch goes down. The standby switch does not handle any of the workload besides MultiChassis Etherchannels.

Question 5

What is a VSL?

Answer 5

Virtual switch link. It’s the link that the standby and active switch use to communicate. The VSL is also an etherchannel.

Question 6

What is a MultiChassis Etherchannel?

Answer 6

An etherchannel consisting of bundled ports on both the active and the standby switch.

Question 7

What two pieces of VSS create the super-fast redundancy?

Answer 7

SSO (stateful switchover) and NSF (non-stop forwarding)

Question 8

How do you enable SSO and NSF?

Answer 8

They are enabled by default when VSS is configured.

Question 9

How does the standby switch detect if the active switch has gone down?

Answer 9

Via the VSL.

Question 10

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?

Answer 10

It will not resume the active switch role. Instead, it will become the “new” standby switch.

Question 11

What is a dual-active situation, and what causes it?

Answer 11

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.

Question 12

What is dual-active recovery?

Answer 12

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.

Question 13

According to Cisco, what is VSS meant to replace?

Answer 13

First hop redundancy protocols (VRRP, GLBP, HSRP, etc.)

Question 14

What is the function of NSF?

Answer 14

provide nonstop forwarding in the event of failure of one of the member supervisors

Question 15

Which statement describes what happens if all VSL connections between the virtual switch members are lost?

Answer 15

The VSS transitions to the dual active recovery mode, and only the new active virtual switch continues to forward traffic.

Question 16

Which statement describes what happens when a switch enters dual active recovery mode?

Answer 16

All interfaces are shut down in the formerly active virtual switch member, but the new active virtual switch forwards traffic on all links.

Question 17

Which option is a benefit of using VSS?

Answer 17

removes the need for a First Hop Redundancy Protocol

Question 18

what does the RP do?

Answer 18

receives the first packet of a traffic flow and routes it

Question 19

what does the SP do?

Answer 19

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

Question 20

When it comes to switch redundancy, what is NSF?

Answer 20

Non-Stop Forwarding. It is a method that focuses on rebuilding the Routing Information Base after a supervisor switch-over.

Question 21

What are the fail-over times for the following redundancy modes: RPR, RPR+, SSO?

Answer 21

-RPR >2minutes-RPR+ >30seconds-SSO >1second

Question 22

What routing protocols are supported by NSF?

Answer 22

-BGP, EIGRP, OSPF, IS-IS

Question 23

What are the three redundancy modes used on Catalyst switches with more than one supervisor?

Answer 23

-RPR(Route Processor Redundancy ->Cold standby)-RPR+(Route Processor Redundancy+ ->Warm standby)-SSO(Stateful Switch Over ->Hot standby)

Question 24

What does VSS stand for?

Answer 24

Virtual Switching System

Question 25

What is *VSS*?

Answer 25

VSS combines two 6500 series switches into a single virtual switch.

Question 26

What are the benefits of *VSS*?

Answer 26

VSS has the same general benefits as stackwise, which is single point of management, redundancy, and multi-chassis etherchannel

Question 27

What are the differences between *VSS* and *Stackwise*?

Answer 27

Stackwise required all members to be co-located due to them needing a special short cable to connect. VSS switches are connected via a standard 10GB Ethernet. The interlink can even support etherchannel.

Question 28

What is the *VSS Active Chassis*?

Answer 28

The Active Chassis in VSS runs the layer 2 and layer 3 control protocols and provides the console interface.

Question 29

What does *VSL* stand for?

Answer 29

Virtual Switch Link

Question 30

What is VSL?

Answer 30

VSL is the physical connection between the two chassis in VSS. Carries both control and data traffic between the two chassis.

Question 31

What does VSLP stand for?

Answer 31

Virtual Switch Link Protocol

Question 32

What is VSLP?

Answer 32

VSLP is composed of two sub-protocols, LMP and RRP. The former provides domain identity parameters and capabilities, while the latter determines which chassis becomes VSS active.

Question 33

What does *LMP* stand for?

Answer 33

Link Management Protocol

Question 34

What does *RRP* stand for?

Answer 34

Role Resolution Protocol