CDL Section 7 - Employing Programmability on Cisco Platforms

Question 1

There are 4 main types of Network Programmability options today:

1. programmable APIs - the control and data planes are still in the same box, the same as in a traditional approach; EX) API on a DC switch
2. pure SDN - control plane has been separated to a controller and only the data plane is on the device; most popular method here is NETCONF

Answer 1

3. Hybrid SDN - control plane is still needed on the network devices so that it can independently run some network protocols, like routing. There is also a controller.
4. overlay network - existing devices are kept intact and that a virtual network using overlays is created; EX) is VXLAN in an SDA environment, or SDWAN

Question 2

REVIEW:
→ Network Automation - the process of automating the configuring, managing, testing, deploying, and operating of physical and virtual devices within a network.

Main use cases for network automation are:

Answer 2

○ Device provisioning
○ Device SW management
○ Compliance checks 
○ Reporting
○ Troubleshooting
○ Data collection on network devices
○ Telemetry on network behavior

Question 3

What types of APIs does the IOS-XE programmable interface support?

Answer 3

NETCONF, RESTCONF, gRPC

Question 4

Does IOS-XE streaming telemetry use a push or pull method for data?

Answer 4

Push

It allows pushing data off the device to an external collector at a much higher frequency more efficiently, and “data-on-change” streaming – DNAC

Question 5

What are the 3 operational approaches in a production environment to programmatically integrate or configure a network device?

Answer 5

1. via a controller (DNAC); has north and southbound interfaces
2. via config management tools (DevOps)
3. Directly on the device

Question 6

In what language is the configuration of NETCONF modeled in?

Answer 6

YANG

It used to be just CLI over NETCONF

Question 7

What is Guest Shell? (running on an IOS-XE based switch for example)

What does the Guest Shell allow?

Answer 7

A Guest Shell container is a built-in Linux Container (LXC) running on Cisco IOS XE systems with Python version 2 preinstalled.

IOS XE Software running on a Cisco Catalyst 9000 switch reserves dedicated memory and CPU resources for Guest Shell.

Guest Shell, a specialized container that is prebuilt and installed within the system, allows customers and third-party application developers to add custom functionality directly on the device in a secure, isolated environment.

Question 8

REVIEW: NXOS Device-Level APIs

1. NX-API CLI - makes CLI available outside of the switch (versus on-box). Sends commands to the device wrapped in HTTP/S but gets structured XML/JSON data back
2. NX-API REST - provides access to objects stored in the Management Information Tree (MIT), which maintains the objects on a switch (configuration, operational status, statistics, faults, etc. are all objects)
   * The MIT is the single source of truth for the configuration and operational status of NX-OS features and elements

Answer 8

3. NX-SDK - a simple & powerful tool for providing off-box, 3rd party custom app development to be placed/run on Nexus switches
4. Guest Shell - built-in Linux Container (LXC) running on Nexus devices.
5. Bash (Bourne Again Shell) - allows you to access the underlying Linux system on the device and manage the system that way.