Home > Articles > Automation


Chapter Description

This sample chapter from Cisco Certified DevNet Professional DEVCOR 350-901 Official Cert Guide maps to the second part of the Developing Applications Using Cisco Core Platforms and APIs v1.0 (350-901) Exam Blueprint Section 5.0, ''Infrastructure and Automation.''


RESTful APIs (or representational state transfer APIs) use Web/HTTP services for read and modification functions. This stateless protocol has several predefined operations, as seen in Table 10-5. Because it’s a stateless protocol, the server does not maintain the state of a request. The client’s request must contain all information needed to complete a request, such as session state.


Table 10-5 REST API Operation Types




Safety/Read-only Function


Reads resource data, settings




Tests the API endpoint for validity, accessibility, and recent modifications; similar to GET without response payload




Creates a new resource




Updates or replaces a resource




Modifies changes to a resource (not complete replacement)




Deletes a resource




Starts communications with the resource; opens a tunnel




Provides information about the capabilities of a resource, without initiating a resource retrieval function



API Methods

Another important aspect of a RESTful API is the API method’s idempotency, or capability to produce the same result when invoked, regardless of the number of times. The same request repeated to an idempotent endpoint should return an identical result regardless of two executions or hundreds.

API Authentication

Authentication to a RESTful API can take any number of forms: basic authentication, API key, bearer token, OAuth, or digest authentication, to name a few. Basic authentication is common, where the username is concatenated with a colon and the user’s password. The combined string is then Base64-encoded. You can easily generate the authentication string on macOS or other Linux derivatives using the built-in openssl utility. Windows platforms can achieve the same result by installing OpenSSL or obtaining a Base64-encoding utility.

Example 10-3 shows an example of generating a basic authentication string with openssl on macOS.

Example 10-3 Generating Base64 Basic Authentication String on MacOS

Mac ~ % echo -n 'myusername:DevNet4U!' | openssl base64
Mac ~ %

This method is not considered secure due to the encoding; at a minimum, the connection should be TLS-enabled so that the weak security model is at least wrapped in a layer of transport encryption.

Either API key or bearer token is more preferable from a security perspective. These models require you to generate a one-time key, usually from an administrative portal or user profile page. For example, you can enable the Meraki Dashboard API by first enabling the API for your organization: Organization > Settings > Dashboard API access. Then the associated Dashboard Administrator user can access the My Profile page to generate an API key. The key can also be revoked and a new key generated at any time, if needed.

API Pagination

API pagination serves as a method to protect API servers from overload due to large data retrieval requests. An API may limit return results, commonly rows or records, to a specific count. For example, the DNA Center REST API v2.1.2.x limits device results to 500 records at a time. To poll inventory beyond that, you would use pagination:

GET /dna/intent/api/v1/network-device/{index}/{count}

For example, if you had 1433 devices in inventory, you would use these successive polls:

GET /dna/intent/api/v1/network-device/1/500

GET /dna/intent/api/v1/network-device/501/500

GET /dna/intent/api/v1/network-device/1000/433

Other APIs may provide different cues that pagination was in effect. The API return results may include the following parameters:

Records: 2034

First: 0

Last: 999

Next: 1000

Payload Data Formats JSON XML

When dealing with REST APIs, you often need to provide a request payload containing parameters. The parameters could be anything—username to provision, interface name to poll, operating system template for a virtual machine. The API response payload body likewise has information to be consumed. In either case, it is common to work with XML- or JSON-formatted data, although others are possible and less common. These two data encoding models are conducive to programmatic use.



The Extensible Markup Language (XML) is a markup language and data encoding model that has similarities to HTML. It is used to describe and share information in a programmatic but still humanly readable way.

XML documents have structure and can represent records and lists. Many people look at XML as information and data wrapped in tags. See Example 10-4 for context.

Example 10-4 XML Document

         <Location>San Jose, CA</Location>
               <Description>Uplink to Switch-BB</Description>
               <Description />

In this example, the structure of this XML document represents a router record. <Document>, <Nodes>, <Node>, <Name>, and <Location> are some of the tags created by the document author. They also define the structure. Router-A, San Jose, CA, and GigabitEthernet0/0/0 are values associated with the tags. Generally, when an XML document or schema is written, the XML tags should provide context for the value(s) supplied. The values associated with the tags are plaintext and do not convey data type. As a plaintext document, XML lends well to data exchange and compression, where needed.

XML has a history associated with document publishing. Its functional similarity with HTML provides value: XML defines and stores data, focusing on content; HTML defines format, focusing on how the content looks. The Extensible Stylesheet Language (XSL) provides a data transformation function, XSL Transformations (XSLT), for converting XML documents from one format into another, such as XML into HTML. When you consider that many APIs output results in XML, using XSLTs to convert that output into HTML is an enabling feature. This is the basis for simple “API to Dashboard” automation.

Referring to Example 10-4, you can see that XML documents contain starting tags, such as <Node>, and ending (or closing) tags, such as </Node>. There is also the convention of an empty element tag; note the <Description /> example. All elements must have an end tag or be described with the empty element tag for well-formed XML documents. Tags are case sensitive, and the start and end tags must match case. If you’re a document author, you are able to use any naming style you wish: lowercase, uppercase, underscore, Pascal case, Camel case, and so on. It is suggested that you do not use dashes (-) or periods (.) in tags to prevent misinterpretation by some processors.

All elements must be balanced in nesting, but the spacing is not prescribed. A convention of three spaces aids the reader. It is acceptable for no spacing in a highly compressed document, but the elements must still be nested among start and end tags.

XML can have attributes, similar to HTML. In the HTML example <img src="devnet_logo.png" alt="DevNet Logo" />, you can recognize attributes of src and alt with values of "devnet_logo.png" and "DevNet Logo". Similarly, in XML, data can have attributes—for example, <interface type="GigabitEthernet">0/0/0</interface>.

Attribute values, such as “GigabitEthernet”, must be surrounded by double quotes. Values between tags, such as 0/0/0, do not require quotes.

XML documents usually start with an XML declaration or prolog to describe the version and encoding being used, but it is optional:

<?xml version="1.0" encoding="UTF-8"?>

XML documents are often described as trees composed of elements. The root element starts the document. Branches and child elements define the structure with elements potentially having subelements, or children. In Example 10-4, the root element is <Document>. Because XML does not predefine tags, you may see other root element tags. Some common ones are <Root>, <DocumentRoot>, <Parent>, and <rootElement>. It is up to the document author to define the tags and structure.

The <Nodes> element is a child. The <Node> elements are also children. The <Node> elements are also siblings to each other, as a list of records. The <Name>, <IPv4Address>, <IPv4NetMask>, and <Description> elements are children to <Node>, siblings to each other and form a record. Because there are multiple <Node> elements, a list is formed.

XML documents can be viewed in browsers, typically through an Open File function. The browser may render the XML with easy-to-understand hierarchy and expand or collapse functions using + and -or ^ and > gadgets. See Figure 10-13 for another example of ACI XML data, rendered in a browser.

Figure 10.13

Figure 10.13 ACI XML Data Rendered in Browser



JavaScript Object Notation (JSON) is a newer data encoding model than XML and is growing in popularity and use with its more compact notation, ease of understanding, and closer integration with Python programming. It is lightweight, self-describing, and programming language independent. If your development includes JavaScript, then JSON is an easy choice for data encoding with its natural alignment to JavaScript syntax.

The JSON syntax provides data being written as name-value pairs. Data is separated by commas. Records or objects are defined by curly braces { }. Arrays and lists are contained within square brackets [ ].

The name of a name-value pair should be surrounded by double quotes. The value should have double quotes if representing a string. It should not have quotes if representing a numeric, Boolean (true/false), or null value. See Example 10-5 for a sample JSON record.

Example 10-5 REST API Payload as JSON

   "Document": {
      "Nodes": {
         "Node": {
            "Name": "Router-A",
            "Location": "San Jose, CA",
            "InterfaceCount": 2,
            "Interfaces": {
               "Interface": [
                     "Name": "GigabitEthernet0/0/0",
                     "IPv4Address": "",
                     "IPv4NetMask": "",
                     "Description": "Uplink to Switch-BB",
                     "isConnected": true
                     "Name": "GigabitEthernet0/0/1",
                     "IPv4Address": "",
                     "IPv4NetMask": "",
                     "Description": null,
                     "isConnected": false

Using this example, you can compare the structure with the previous XML representation. There is a list of interfaces; each interface is a record or object.

With APIs, the system may not give you a choice of data formatting; either XML or JSON may be the default. However, content negotiation is supported by many APIs. If the server drives the output representation, a Content-Type header shows “application/xml” or “application/json” as the response body payload type.

If the requesting client can request what’s desired, then an Accept header specifies similar values for preference. With some APIs, appending .xml or .json to the request URI returns the data with the preferred format.

6. Cross-Domain, Technology-Agnostic Orchestration (CDTAO) | Next Section Previous Section

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020