The Cisco DNA Center controller expects all incoming data from the REST API to be in JSON format. It is also important to note that the HTTP POST function is used to send the credentials to the Cisco DNA Center controller. The Cisco DNA Center appliance uses basic authentication to pass a username and password to the Cisco DNA Center Token API to authenticate users. This API is used to authenticate a user to the Cisco DNA Center controller to make additional API calls. Just as users do when logging in to a device via the CLI, if secured properly, they should be prompted for login credentials. The same method applies to using an API to authenticate to software.
The Following are the Steps:
Step 1. In the URL bar, enter https://sandboxdnac.cisco.com/api/system/v1/auth/ token to target the Token API.
Step 2. Select the HTTP POST operation from the dropdown box.
Step 3. Under the Authorization tab, ensure that the type is set to Basic Auth.
Step 4. Enter devnetuser as the username and Cisco123! as the password.
Step 5. Select the Headers tab and enter Content-Type as the key. Step
Step 6. Select application/json as the value.
Step 7. Click the Send button to pass the credentials to the Cisco DNA Center controller via the Token API.
Setting Up Postman to Authenticate with the Cisco DNA Center Controller
You need a token for any future API calls to the Cisco DNA Center controller. When you are successfully authenticated to the Cisco DNA Center controller, you receive a token that contains a string that looks similar to the following:
“eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiI1YTU4Y2QzN2UwNWJiYTAwOGVmNjJiOT IiLCJhdXRoU291cmNlIjoiaW50ZXJuYWwiLCJ0ZW5hbnROYW1lIjoiVE5UMCIsInJvbGVzIjpbIjVhMz E1MTYwOTA5MGZiYTY5OGIyZjViNyJdLCJ0ZW5hbnRJZCI6IjVhMzE1MTlkZTA1YmJhMDA4ZWY2 MWYwYSIsImV4cCI6MTUyMTQ5NzI2NCwidXNlcm5hbWUiOiJkZXZuZXR1c2VyIn0.tgAJfLc1OaUwa JCX6lzfjPG7Om2x97oiTIozUpAzomM”
Think of it as a hash that is generated from the supplied login credentials. The token changes every time authentication is made to the Cisco DNA Center controller. It is important to remember that when you are authenticated, the token you receive is used only for the current authenticated session to the controller. If another user authenticates via the Token API, he or she will receive a unique token to be able to utilize the API based on his or her login credentials.
Cisco DNA Center POST Operation
You can see in the top right of the screen shown in Figure 28-8 that the received HTTP status code from the Cisco DNA Center controller is 200 OK. Based on the list in Table 28-5, you can tell that the HTTP status code 200 means that the API call was completed successfully. In addition, you can see how long it took to process the HTTP POST request: 980 ms. Now we can take a look at some of the other available API calls. The first API call that is covered in this section is the Network Device API, which allows users to retrieve a list of devices that are currently in inventory that is being managed by the Cisco DNA Center platform controller.
Step 1. Copy the token you received earlier and click a new tab in Postman.
Step 2. In the URL bar enter https://sandboxdnac.cisco.com/api/v1/network-device to target the Network Device API.
Step 3. Select the HTTP GET operation from the dropdown box.
Step 4. Select the Headers tab and enter Content-Type as the key.
Step 5. Select application/json as the value.
Step 6. Add another key and enter X-Auth-Token.
Step 7. Paste the token in as the value.
Step 8. Click Send to pass the token to the Cisco DNA Center controller and perform an HTTP GET to retrieve a device inventory list using the Network Device API.
Postman Setup for Retrieving the Network Device Inventory with an API Call
Based on the response received from the Cisco DNA Center controller, you can see the HTTP status code 200 OK, and you can also see that a device inventory was received, in JSON format.
Device Inventory Pulled Using a Network Device API Call in Postman
By now you should see how powerful APIs can be. Within a few moments, users are able to gather a tremendous amount of information about the devices currently being managed by the Cisco DNA Center controller. In the time it takes someone to log in to a device using the CLI and issue all the relevant show commands to gather data, an API call can be used to gather that data for the entire network. APIs give network engineers time to do other things!
When using APIs, it is common to manipulate data by using filters and offsets. Say that a user wants to leverage the Network Device API to gather information on only the second device in the inventory. This is where the API documentation becomes so valuable. Most APIs have documentation that explains what they can be used to accomplish.
In Postman, it is possible to modify the Network Device API URL and add ?limit=1 to the end of the URL to show only a single device in the inventory. It is also possible to add the &offset=2 command to the end of the URL to state that only the second device in the inventory should be shown. These query parameters are part of the API and can be invoked using a client like Postman as well. Although it may sound confusing, the limit keyword simply states that a user only wants to retrieve one record from the inventory; the offset command states that the user wants that one record to be the second record in the inventory.
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