VDC - [Part 1] - INTERVIEW QUESTIONS

Question - 1 What are the purpose and role of VDC in Nexus ?

• Cisco Nexus has a feature of VDC (Virtual Device Context), by which you can divide a single physical Nexus Switch into two or more logical switches. These logical switches will perform as independent switches. 
• So we can manage multiple logical devices in a single physical device. These logical switch behaves same like physical switch. Each logical switches have separate administration and operational capability.
• VDCs also virtualize the control plane, like RIB (Routing Information Base ) and the routing protocols.
• Each Virtual Device Context (VDC) has its own unique set of L2 and L3 process, which will run on each of logical switches. 
• Each logical switch has its own configuration,  which is stored in NVRAM via VDC name.
• Each logical devices has its own L2 and L3 control plane like in each physical switch.
• Only Nexus 7K (7000, 7700) series platform support the VDC

Question - 2 Explain the benefits of VDC ?

• Fault Isolation - VDC provides fault isolation facility. If any issue will occurs in any L2 or L3 process, then it will not be affect any other processes, which is running on other logical switches.
• Management Isolation - We can manage multiple logical devices in a single physical device. These logical switch behaves same like physical switch. Each logical switches have separate administration and operational capability. It can be accessed by unique individual IP.
• Hardware Isolation - If any hardware resource will be allocated to any VDC, then it will be part of that particular VDC, administrator can be assigned it to any other VDC.
• Separation Of Data Traffic - It provides separation of data traffic at VDC level
• Enhance Security - It Provide enhance Security at VDC level.

Question - 3 How many types VDC does support by Nexus ?

• Below types of VDC supported by Nexus Switch:

1. Default VDC
2. Non –Default VDC
3. Admin VDC
4. Storage VDC

Note - Click here to know more about  VDC types

Question - 4 How many VDC can we create on a Nexus Switch ?

• Number of the VDC per nexus switch depends on the supervisor model.

1. SUP1 module - 4 non-default VDC and one admin VDC. OR 3 non-default VDC and 1 default VDC
2. SUP2 module - 1 admin VDC and 4 non-default VDCs.
3. SUP2E module - 1 admin VDC and 8 non-default VDCs
4. SUP3E module - 8+1 admin VDC

Question - 5 Which switch resources that can be allocated or not allocated to VDC ?

Resources that Can Be Allocated to a VDC- 

• Physical Interfaces
• Port-Channels
• Bridge Domains
• VLANs (Virtual Local Area Network)
• VPC (Virtual Port Channel)
• HSRP (Hot Standby Routing Protocol)
• GLBP (Gateway Load Balancing Protocol) Group IDs
• SPAN (Switched Port Analyzer)

Resources that Cannot Be Allocated to a VDC- 

• CPU
• Memory
• TCAM (Ternary Content-Addressable Memory) Resources like FIB, QoS, Security ACLs

Question - 6 Which components of switches will be shared between VDC ?

• A single instance of the kernel which supports all of the processes and VDCs.
• Fabric modules
• Supervisor modules
• Fan trays
• System fan trays
• Power supplies
• Hardware SPAN (Switched Port Analyzer) resources
• CoPP (Control Plane Policing)
• CMP (Connectivity Management Processor)

Question - 7 Explain types of resources in Nexus VDC.

Basically three types of resources uses in VDC

1. Global Resources - Resources which configured or allocated to all VDCs for the master VDC are known as Global Resources. Example -  Boot image configuration, CoPP (Control Plane Policing).
2. Dedicated Resources - Resources which configured or allocated to a particular VDC are known as dedicated resources. Example - L2 Ports, L3 ports, VLANs, IP address.
3. Shared Resources - Resources which shared between VDCs are known as Shared Resources. Example - OOB Ethernet, Management port.

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Anubhav Upadhyay

Hello and welcome to networktopic Blog. My name is Anubhav. I am a Senior Network Egineer. I have created this blog specially to serve interview questions and answer on Network Routing and Switching, I will try my best to serve correct and updated networking knowledge for you as per my corporate experience.

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