SD WAN Interview Questions

Introduction

As businesses grow in digital transformation, Software-Defined Wide Area Networking (SD-WAN) has emerged as a critical technology for optimizing network performance and connectivity. With the growing demand for SD-WAN expertise, professionals seeking careers in this field must be well-prepared for interview questions that assess their knowledge and skills. This blog presents the top 20 SD-WAN interview questions and answers for 2024.

Without further delay, let’s start with our Most Asked SD WAN Questions and Answers.

Commonly Asked SD WAN Interview Questions

1. What is SD WAN?

Ans: SD WAN (also known as Cisco SD WAN) is a cloud-based service that provides secure, flexible, and rich service architecture. It offers an enhanced way to manage and use WAN with cloud-based applications like Microsoft Office 365 and public cloud services like Azure. 
 

2. What are the advantages of SD WAN?

Ans: The advantages of SD WAN are:

(i) Simplicity - Network managers can easily control a network since it is deployed as a software.

(ii) Better performance - SD WAN provides a better user experience. This is because the application can be deployed in a short time, providing a consistent user experience. 

(iii) Reduced cost - SD WAN uses only software. Traditional WANs uses routers. Thus, there is a reduction in the price due to the absence of hardware components. 

(iv) Security features - SD WAN securely connects users to the application. It also protects the data on the WAN side and in the cloud. 
 

3. Which industries use Cisco SD WAN?

Ans: Some industries that use SD WAN are:

(i) Retail industry uses SD WAN to help quickly set up new stores.

(ii) Manufacturing industry benefits from the enhanced security features in SD WAN to protect their data from the suppliers’ networks.

(iii) Public and private events use SD WAN to control the network traffic due to a considerable number of people using a network. 

(iv) Financial firms use SD WAN for their security features.

(v) Healthcare centers are equipped with IoT devices. These require an efficient network management system like SD WAN. 
 

4. Name two companies that use SD WAN.

Ans: Two companies that use SD WAN are Fortune 2000 and Cisco.
 

5. What are vSmart controllers?

Ans: vSmart controllers are the central part of SD WAN. It makes the policies and connections between the branches in SD WAN. This includes tasks like modifying the routing information, access control, etc. 
 

6. What are vBond orchestrators?

Ans: A vBond orchestrator is a tool that helps with the initial setup of SD WAN. It authenticates and authorizes elements in the network and specifies how each component of the network will communicate with each other. 
 

7. What is vManage controller?

Ans: A vManage controller is a centralized tool in SD WAN that controls the whole network and its security functions through a dashboard. It is the basic structure that performs all the other tasks of SD WAN. 
 

8.  Does SD WAN support network segmentation?

Ans: SD WAN supports network segmentation. Segmentation is a feature that allows “secure logical isolation” of the elements in SD WAN as distinct Virtual Private Networks (VPNs). SD WAN centrally controls these segments. 
 

9. What are the benefits of network segmentation?

Ans: The benefits of network segmentation are:

(i) It provides better security features by establishing secure separation into multiple application segments. 

(ii) Centralized policies control the network which company can access which segments.

(iii) Guest Wi-fi is kept in low priority sections until they are transferred to the Internet at the nearest exit points.

(iv) Different segments can be made for different business partners, keeping their information and accessibility separate.

(v) Central policies control a business partner’s access to data, establishing a secure connection. 
 

10. What security capabilities does SD WAN have?

Ans: The security capabilities of SD WAN include functions like application-aware firewall, intrusion prevention, DNS layer enforcement (known as Cisco Umbrella), and URL filtering.  
 

11. What are the elements in SD WAN?

Ans: The elements in SD WAN are:

(i) vSmart Controller - Central unit which controls all the functions of SD WAN.

(ii) vManage Controller - Central dashboard for managing and configuring SD WAN.

(iii) vEdge Router - IP routers that perform standard routing policies and overlay communication.

(iv) vBond Orchestrator - Initially authenticates, authorizes and connects the elements in SD WAN. 
 

12. What is site-id?

Ans: The site-id is a Unicode number used to identify the branch office, data center, or campus in the overlay network in SD WAN (known as a site). 
 

13. Does SD WAN support multi-tenancy?

Ans: Multi-tenancy means a service provider’s ability to manage multiple customers efficiently. SD WAN can support multi-tenancy using the vManage controller. Each tenant shares a vBond orchestrator and the service provider’s domain name. 
 

14. What is DevNet ecosystem exchange?

Ans: DevNet ecosystem exchange is an online portal that allows applications built using SD WAN for Cisco platforms to be shared. This helps business leaders and developers find partner solutions running on Cisco platforms and products.
 

15. What is DevNet code exchange?

Ans: DevNet code exchange is a platform where developers can access and share software. It contains sample code, adaptors, tools and software development kits (SDKs) written by Cisco and the DevNet community. 

16. What problems can Cisco SD WAN overcome?

Ans: A few problems that SD WAN can overcome are:

(i) Provide a transport-independent and low-cost WAN

(ii) Protect the most critical resources of an organization

(iii) Provide optimal user experience
 

17. Is an SD WAN solution secure?

Ans: SD WAN is built on a zero-trust concept. This means that a multilayer security secures data at every point in the network so there can be no unauthorized access. The network engineer must give all edge devices prior authorization to access the network. Each packet in the control, data, and management planes is secured with Secure Socket Layer (SSL) and IP security (IPsec) technologies. 
 

18. Which platforms support the security features in SD WAN?

Ans: The platforms supporting the security features in SD WAN are:

19. What specifications are required for Zero Touch Provisioning (ZTP)?

Ans: In the hardware-based vEdge appliance, only some ports can be used for ZTP. The specifications of those ports are:

(i) The Gateway Router should be accessible to the public DNS servers and capable of accessing stp.viptela.com. 

(ii) There must be an appropriate device configuration template in vManage for the vEdge router connected to the vEdge device. 

(iii) The system IP address and side ID must be a part of the device configuration template. 
 

20. Can SD WAN provide optimization for IaaS (Infrastructure as a service) and SaaS (software as a service) platforms like AWS, Microsoft Azure and Office 365, etc.?

Ans: SD WAN does provide optimization for IasS and SaaS platforms with Cisco Cloud OnRamp in the vEdge series platform. Cloud OnRamp continuously measures the performance of an application through the permissible paths from a branch, while SD WAN makes real-time decisions on the best-performing path. Businesses can then deploy whichever program suits their business and security needs.   
 

21. Is SD WAN programmable, and does it support APIs?

Ans: Yes, SD WAN is open and programmable with open APIs. This means that SD WAN allows its users to create new and unique services. SD WAN also gives access to available Representational State Transfer (REST) APIs, enables users to generate API calls, obtain device and interface information using code, pass parameters and write applications, and work on new solutions. All this is done using DevNet Ecosystem Exchange and DevNet Code Exchange. 
 

22. Name the latest software release version for Cisco XE SD WAN supported on Cisco 1000 and 4000 series ISRs, ASR 1000 and 5000 series ENCS platforms?

Ans: The latest software release is Cisco IOS XE SD WAN Software Release 16.11.1.
 

23. What are the different Overlay Management Protocol (OMP) routes?

Ans: OMP routes are protocols that establish connections between the endpoints of OMP-orchestrated transport networks. They are of different types as follows:

(i) OMP routes - These are TCP-based protocol that maintains the SD WAN control plane. They establish connections for forwarding between the vEdge routers and vSmart controllers and between the controllers themselves. 

(ii) Transport Locations (TLOCs) -  These identifiers connect an OMP route to a physical location. They are accessible through entries in the routing table. They act as the next hop for OMP routes.

(iii) Service routes - These are the elements that connect an OMP route to a service in a network. The services here may be firewalls, intrusion detection systems (IDPs), and load balancers. 

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24. How is Cisco SD WAN deployed at branch offices, data center networks, and regional hubs?

Ans: SD WAN can be deployed at branch offices, data center networks, and regional hubs by virtual or physical secure routers. After deployment, they can then use the services like WAN optimization and firewall or basic WAN connectivity over physical or virtual modes as mentioned below:

(i) Physical modes - 

• Branch Cisco vEdge Series Routers
• Branch Cisco 1000 Series Integrated Services Routers (ISR)
• Branch Cisco 4000 Series ISR
• Branch or Regional Hub/Data Center - Cisco ASR 1000 Series Aggregation Services Routers (ASR)
   

(ii) Virtual modes - 

• SD Branch Cisco
• 5000 Series Enterprise Network Compute System (ENCS) and ISR virtual (ISRv) router
• Network Hub/colocation/data center - Cisco Cloud Services Platform 5000 and Cloud Services Router 1000V (CSR1000V)
   

(iii) Public Cloud modes (IaaS) -

• Amazon Web Services
• Microsoft Azure
• Google Cloud Platform 
   

25. How does SD WAN help in architectural transformation?

Ans: SD WAN helps in architectural transformation in the following ways:

(i) Transport Independence - SD WAN creates a service separate from physical networks. This gives transport independence since the network is not associated with any service

(ii) Secure Routing Scale - SD WAN provides security features through encryption and device authentication. 

(iii) Network Wide Segmentation - A network is segmented into multiple logical topologies by an organization. Each of these individual segments is separately encrypted, thereby providing enhanced security.

(iv) Centrally Enforce Policy and Business Logic - Each network location has a centralized controller that enforces policies and business logic. 

(v) Inserts Layer 4-7 Services on Demand - SD WAN allows layers 4-7 (transport, session, presentation, application) to be made using third-party applications. 
 

26. What are a domain and a domain ID?

Ans: A domain is a logical group of vEdge routers and vSmart controllers that marks the region of control of a vSmart controller. In a domain, vEdge routers can only connect with vSmart controllers in their domain. A vBond orchestrator knows which vSmart controller is in which domain. So, when a new vEdge router is added, the vBond orchestrator links the router with its appropriate controller. 

Each domain is labeled by a unique integer known as a domain ID. One overlay network can have only one domain ID. 
 

27. What is transport location (TLOC)?

Ans: A transport location (TLOC) is an identifier that connects an OMP route to a physical location. This physical location may be a WAN transport network or a Network Address Translation (NAT) gateway. TLOC are accessible through entries in the routing table and act as the next hop for OMP routes. They are identified by an IP address-color pair written as a tuple {IP-address, color}, where the IP address is the system’s IP address, and the color represents a VPN or the traffic flow within a VPN. 
 

28. What is a zero-touch provisioning (ZTP) process?

Ans: When a vEdge router is powered for the first time, it tries to connect with the ZTP server through the hostname ztp.vipela.com. There, the vEdge router gets its vBond orchestrator information. After that, it makes the necessary connections for configuration to join the overlay network.