Mastering Cisco VSS Interview Questions: A Comprehensive Guide

In the ever-evolving world of networking, Cisco’s Virtual Switching System (VSS) has emerged as a powerful solution for enhancing network resilience, scalability, and performance. As businesses increasingly rely on robust and efficient network infrastructures, the demand for professionals with expertise in VSS has skyrocketed. If you’re aspiring to secure a role in this domain, it’s essential to be well-versed in the intricacies of VSS and prepared to tackle the most commonly asked interview questions.

This comprehensive guide will equip you with the knowledge and insights needed to ace your Cisco VSS interview. We’ll delve into a wide range of topics, from fundamental concepts to advanced design and troubleshooting scenarios, ensuring you’re ready to showcase your skills and impress potential employers.

Understanding the Basics of Cisco VSS

Before diving into the interview questions, let’s lay the foundation by understanding the core concepts of Cisco VSS:

• What is VSS? Cisco Virtual Switching System (VSS) is a technology that allows two physical switches to operate as a single logical entity, providing high availability, scalability, and simplified management.
• Benefits of VSS: VSS offers various benefits, including non-stop forwarding, stateful switchover, enhanced fault tolerance, and increased port density.
• Minimum Software Requirements: To implement VSS, the minimum software requirement is Cisco IOS Software Release 12.2(33)SXI or later.
• Number of Switches: A VSS can consist of two Cisco Catalyst 6500 Series Switches operating in a single logical entity.

With a solid grasp of these fundamentals, you’re ready to dive deeper into the most commonly asked Cisco VSS interview questions.

Common Cisco VSS Interview Questions and Answers

1. What is the benefit of VSS?

The primary benefit of VSS is increased operational continuity and resilience. By combining two physical switches into a single logical entity, VSS provides features such as non-stop forwarding, stateful switchover, and enhanced fault tolerance. Additionally, VSS simplifies network management by allowing administrators to manage the two switches as a single entity.

1. What is VSS1440?

VSS1440 is a specific implementation of VSS that combines two Cisco Catalyst 6500-E Series Switches with dual-chassis 1440 Gbps logical switching capacity. This configuration provides high-density, high-performance, and resilient switching for enterprise and service provider networks.

1. What is the recovery process in case of a Dual Active Scenario?

In a Dual Active Scenario, where both switches in the VSS domain assume the active role, the recovery process involves the following steps:

• Detection: The Dual Active Scenario is detected by the switches using various mechanisms, such as the Dual Active Detection (DAD) protocol or external monitoring tools.
• Recovery: Once detected, the recovery process begins. One switch is elected as the active switch, and the other switch is reset and reloaded to become the standby switch.
• Synchronization: After the reload, the standby switch synchronizes its configuration and state with the active switch.

1. Can I check the serial number of the standby switch in a VSS?

Yes, you can check the serial number of the standby switch in a VSS using the show switch detail command. This command displays detailed information about the switches in the VSS domain, including their serial numbers.

1. Is it mandatory to run any protocol on the Virtual Switch Link (VSL) for communication?

No, it is not mandatory to run a specific protocol on the Virtual Switch Link (VSL) for communication between the switches in the VSS domain. The VSL is a dedicated Ethernet link that carries control and data traffic between the switches. However, it is recommended to use an EtherChannel for increased bandwidth and redundancy.

1. What is the benefit of Quad-SUP in VSS, and in which manner should supervisors be connected?

The benefit of Quad-SUP (Quad-Supervisor) in VSS is increased redundancy and high availability. In a Quad-SUP configuration, each switch in the VSS domain has two supervisors, providing redundancy at the supervisor level.

Regarding the connection of supervisors, it is recommended to connect the supervisors in a cross-stack configuration. This means that the supervisors on one switch should be connected to the supervisors on the other switch in the VSS domain, creating a redundant path for control and data traffic.

1. What is the benefit of MEC (Multichassis EtherChannel)?

The primary benefit of MEC (Multichassis EtherChannel) is increased port density and load sharing across the switches in the VSS domain. MEC allows you to create EtherChannels that span both switches, effectively utilizing the combined port resources of the two switches.

1. What are the MEC failure scenarios?

Some common MEC failure scenarios include:

• VSL Failure: If the Virtual Switch Link (VSL) fails, the MEC will be automatically disabled to prevent network loops.
• Switch Failure: If one switch in the VSS domain fails, the MEC ports on the remaining switch will remain operational, providing continued connectivity.
• Link Failure: If a member link in the MEC goes down, traffic will be redistributed across the remaining links, maintaining connectivity.

1. In case of VSL, if we have configured an EtherChannel between member switches in a VSS with two links of different distances (e.g., 5 km and 25 km), will it affect the VSL?

No, the difference in distances of the links in the VSL EtherChannel should not affect the VSL’s functionality. The VSL is designed to handle varying link lengths and distances, as long as the links meet the necessary latency and bandwidth requirements.

1. What is the difference between the statements “Dual active functionality is enabled” and “Dual active functionality is activated”?

The statement “Dual active functionality is enabled” means that the Dual Active Detection (DAD) feature is configured and ready to detect a Dual Active Scenario.

On the other hand, the statement “Dual active functionality is activated” indicates that a Dual Active Scenario has been detected, and the recovery process has been initiated.

By thoroughly understanding these Cisco VSS interview questions and answers, you’ll be well-prepared to showcase your expertise and impress potential employers. Remember, preparation is key to acing any interview, and this guide provides a solid foundation for mastering the intricacies of Cisco VSS.

Good luck with your interview journey!