What Is JSON and XML in Networking in Networking?
Also known as: JSON and XML in networking, CCNP ENCOR automation, network automation JSON XML, NETCONF vs RESTCONF, YANG data format
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Quick Definition
JSON and XML are ways of organizing data so that computers and network devices can understand each other. JSON uses curly braces and key-value pairs, similar to a simple address book. XML uses tags, like the ones in HTML, to label and structure information. In networking, both formats are used to configure devices, monitor performance, and automate tasks.
Must Know for Exams
The CCNP 350-401 ENCOR exam tests JSON and XML in the Automation and Programmability section, which accounts for about 10 to 15 percent of the exam. Candidates are expected to understand the basic syntax of both formats, compare their characteristics, and know which protocol uses which format. For example, the exam objective clearly states that you must know that NETCONF uses XML and RESTCONF supports both JSON and XML.
You may see a question that shows a snippet of data in JSON or XML and asks you to identify which format it is. Or you might be asked to explain why JSON is preferred over XML in RESTful APIs, with answers referencing verbosity, parsing speed, or human readability. Some questions present a configuration payload and ask you to identify the correct JSON structure that matches a given YANG model.
The exam also tests your ability to interpret error messages related to invalid JSON or XML syntax. For instance, a candidate might be shown a JSON string with a missing comma or an extra curly brace and asked to identify the syntax error. This is why precision matters.
You do not need to be a JSON or XML expert, but you must be comfortable reading and writing basic structures. The exam will not ask you to write a full configuration script, but you might need to interpret part of one. The ENCOR exam also integrates this knowledge with other automation topics like YANG models, NETCONF, RESTCONF, and automation tools like Ansible.
Understanding JSON and XML is the foundation for understanding how these tools communicate with network devices.
Simple Meaning
Imagine you are sending a letter to a friend. You need to write it in a way that your friend can read it. JSON and XML are like two different languages for writing that letter, but both are designed to be clear and organized.
JSON, which stands for JavaScript Object Notation, is like a simple list or a set of labels and answers. For example, if you wanted to describe a network switch, you might write: device type switch, IP address 192.168.
1.1. JSON would write that as device type colon switch comma IP address colon 192.168.1.1 all inside curly braces. It is very clean and easy for both people and computers to read quickly.
XML, which stands for Extensible Markup Language, is more like a formal document with tags. You would write opening tag device type, then switch, then closing tag device type. It is more verbose but very flexible and powerful.
In networking, when a network engineer wants to automate a task, they send a message to a network device like a router or switch. That message must be in a format that both the engineer's script and the device understand. JSON and XML are the most common formats for these messages.
Think of the network device as a mailbox. The engineer writes a message in either JSON or XML, puts it in an envelope using a protocol like RESTCONF or NETCONF, and sends it to the device. The device reads the format, understands the request, and performs the action, like changing a configuration or sending back status information.
JSON is newer and often preferred because it is lighter and faster. XML is older but very widely supported and deeply integrated into many enterprise systems. Both are essential for network automation, which is a key topic in modern Cisco exams like the ENCOR.
Full Technical Definition
JSON and XML are data serialization formats that enable structured information exchange in network programmability and automation. JSON uses a lightweight, text-based format derived from JavaScript object literals. It represents data as key-value pairs and ordered lists, enclosed in curly braces for objects and square brackets for arrays.
For example, a JSON representation of an interface might be: interface name GigabitEthernet0/1, enabled true. This format is concise, human-readable, and easy for machines to parse, making it ideal for RESTful APIs and the RESTCONF protocol. XML is a markup language that uses nested, custom-defined tags to describe data.
It is heavily structured, with opening and closing tags that define elements and attributes. XML supports namespaces, schemas, and validation through Document Type Definitions or XML Schema Definitions. It is the native data format for NETCONF, a network configuration protocol standardized by the IETF.
In networking both formats carry YANG-modeled data. YANG is a data modeling language used to define the configuration and state data of network devices. JSON and XML encode this YANG data so it can be transmitted over the network.
The protocols that transport these formats are RESTCONF, which uses HTTP and JSON or XML, and NETCONF, which uses SSH and XML exclusively. Cisco devices, including routers and switches running IOS XE or IOS XR, support both protocols. When an automation tool like Ansible or a Python script needs to retrieve or modify the configuration of a Cisco device, it sends a JSON or XML payload in an HTTP request to the device's RESTCONF API.
The device parses the payload, validates it against the YANG model, and applies the requested changes. XML is more verbose, meaning it uses more bandwidth and processing power. JSON is more efficient and has become the preferred format for modern APIs.
However, XML remains critical in legacy environments and for NETCONF-based automation. Understanding the syntax, structure, and use cases for both formats is essential for network automation and is tested in the CCNP ENCOR exam under the Automation and Programmability section.
Real-Life Example
Imagine you are a post office manager. You receive thousands of packages every day, and each one must be sorted and delivered to the right house. To do this efficiently, you create a standardized form that every package must include.
This form has fields like sender, recipient, address, and weight. Now, think of two ways to fill out that form. The first way is like JSON. You write a simple card with labels and answers: sender Jane, recipient John, address 123 Oak, weight 5.
It is quick and to the point. The second way is like XML. You write the same information but with tags: open tag sender, Jane, close tag sender, open tag recipient, John, close tag recipient.
This takes more paper but is very formal and leaves no room for confusion. In the networking world, the post office is the network device. The packages are configuration commands or status reports.
The standardized form is the YANG model. JSON and XML are the two formats you can use to fill out that form. When a network automation system sends a request to change the IP address of a router interface, it sends either a JSON or an XML message.
The system chooses JSON because it is lighter and faster. But if the system needs to guarantee that the message is absolutely correct and can be validated against a formal schema, it might choose XML. Both get the job done.
The key is that both formats allow the sender and the receiver to understand each other perfectly, because they both know the structure of the data. That is exactly what JSON and XML provide in networking: a common language for humans and machines to communicate with network devices.
Why This Term Matters
In real IT work, network engineers do not manually log into every switch and router to change configurations. They use automation tools that send requests to devices in mass. These requests must be in a format the device can understand.
JSON and XML are the two standard formats for these requests. If you are an engineer managing a network with hundreds of devices, you will write scripts that push changes to all devices at once. Those scripts will construct JSON or XML payloads.
If you do not understand how these formats work, you cannot correctly write or troubleshoot those scripts. For example, if you have a typo in your JSON syntax, the device will reject the entire configuration change. That could leave a network misconfigured or broken.
Similarly, if you are using a tool like Ansible to automate network tasks, the playbooks you write will often contain JSON or XML data. Understanding the structure allows you to read and modify those playbooks with confidence. In cloud infrastructure, JSON is the default format for APIs used by AWS, Azure, and Google Cloud.
When you query a cloud resource, the response comes back as JSON. You need to parse that JSON to extract information like IP addresses or instance IDs. XML is less common in modern cloud APIs but is still used in some legacy systems and in telecom.
Overall, JSON and XML are not just academic concepts. They are practical tools you use every day if you work with network automation, cloud computing, or any kind of programmable infrastructure. Mastering them is a foundational skill for any IT professional moving into DevOps or NetOps roles.
How It Appears in Exam Questions
Exam questions about JSON and XML in the ENCOR exam fall into several distinct patterns. One common type is format identification. You will be shown a block of text and asked whether it is JSON, XML, or something else.
This tests your basic knowledge of syntax. For example, you might see a snippet with curly braces and colons and know it is JSON. Another snippet with angle brackets would be XML. Another pattern is the compare-and-contrast question.
You could be asked Which of the following is an advantage of JSON over XML? Options might include lighter syntax, native support in NETCONF, or more verbose structure. The correct answer is the lighter syntax.
There are also scenario questions. A question might describe a network engineer who wants to automate the configuration of a Cisco router using RESTCONF. The engineer needs to send a configuration payload.
The question asks which two data formats are supported by RESTCONF. The answer is JSON and XML. Some questions are more technical. You might be given a YANG model and a JSON payload and asked to determine whether the payload correctly represents the model.
This tests your ability to map JSON keys to YANG leaf names and understand data types. Troubleshooting questions are also common. For instance, you are told that a NETCONF session failed because the XML payload was invalid.
You are shown the payload and asked to identify the error, like a missing closing tag. Another pattern involves protocol matching. The question might list data formats and protocols and ask you to match them correctly, such as NETCONF with XML and RESTCONF with JSON and XML.
Some questions use multiple-choice single-answer, multiple-answer, or drag-and-drop formats. For drag-and-drop, you might drag JSON advantages into a box and XML advantages into another. Being comfortable with the syntax and characteristics of both formats is essential to answer these questions correctly.
Study encor
Test your understanding with exam-style practice questions.
Example Scenario
A company called NetCorp has 50 Cisco routers across five branch offices. The network team needs to apply a new VLAN configuration to all routers at once. Instead of logging into each router manually, they use an automation script that sends requests via RESTCONF.
The script builds a payload in JSON format. The JSON payload contains the VLAN ID, the VLAN name, and the interfaces where the VLAN should be applied. One line in the payload reads: vlan-id 100.
The script then uses the RESTCONF API to send this JSON data to the router's management interface. The router receives the payload, validates it against its YANG model, and applies the VLAN configuration. A junior engineer on the team must review the script and confirm that the JSON payload is correct.
The engineer carefully checks every comma, colon, and bracket. They notice that one of the objects has a missing comma after a key-value pair. If that comma were missing, the router would reject the entire payload and the VLAN would not be configured.
The engineer fixes the JSON, and the script runs successfully. This scenario shows exactly how JSON and XML are used in real network automation. The correctness of the data format determines whether the automation succeeds or fails.
Understanding JSON and XML allows the engineer to write, read, and verify automation scripts with confidence.
Common Mistakes
Confusing JSON and XML syntax, such as thinking JSON uses tags or XML uses curly braces.
JSON uses curly braces and colons, while XML uses angle brackets and tags. Mixing them up leads to incorrect payloads that network devices will reject.
Remember that JSON looks like a simple list with curly braces, and XML looks like HTML with angle brackets. Practice reading one line of each until the syntax becomes automatic.
Believing that NETCONF supports both JSON and XML.
NETCONF only supports XML as its native data encoding format. RESTCONF is the protocol that supports both JSON and XML. This distinction is critical for exam questions and real-world protocol selection.
Create a mental rule: NETCONF equals XML only. RESTCONF equals both JSON and XML. Repeat this association when studying protocols.
Assuming JSON is always better than XML in every situation.
JSON is lighter and faster, but XML offers stronger validation through schemas and namespaces. In environments that require strict data validation or compliance, XML may be the better choice.
Think of JSON as fast and flexible, and XML as formal and thorough. Choose the format based on the requirements, not just personal preference.
Ignoring the importance of commas and brackets in JSON, leading to syntax errors.
A single missing comma or extra bracket in JSON makes the entire payload invalid. Network devices return error messages, and the automation fails.
Always use a JSON validator or a linter before sending payloads to devices. In the exam, double-check every piece of punctuation in a JSON snippet.
Exam Trap — Don't Get Fooled
A question asks: Which data format does NETCONF use? The answer choices include JSON, XML, both JSON and XML, and plain text. Memorize that NETCONF is older and standardized with XML as its only data format.
RESTCONF is the newer, more flexible protocol that supports both. Use a simple pairing: NETCONF and XML are a fixed pair, RESTCONF and JSON are a flexible pair.
Commonly Confused With
YANG is a data modeling language used to define the structure of configuration and state data. JSON and XML are the actual data formats that carry that data over the network. Think of YANG as the blueprint and JSON or XML as the materials.
A YANG model defines that an interface has a name and an IP address. The JSON payload then provides the actual values: interface name GigabitEthernet0/1, IP address 192.168.1.1.
RESTCONF is an HTTP-based protocol used to communicate with network devices. JSON and XML are the data formats that RESTCONF uses to transmit information. The protocol is the postman, and the data format is the language the letter is written in.
A Python script sends an HTTP request to a router using RESTCONF. The body of that request is a JSON string containing the new configuration. RESTCONF is the method of delivery, JSON is the content.
NETCONF is another network management protocol that uses SSH for transport and XML exclusively for data encoding. JSON is not used with NETCONF. This is a key distinction from RESTCONF.
If you use NETCONF to configure a router, every message you send must be in XML. You cannot send JSON. If you use RESTCONF, you can choose either JSON or XML.
Step-by-Step Breakdown
Understand the need for structured data
Network devices need configuration data in a predictable, machine-readable format. JSON and XML provide this structure by defining rules for how data is organized, labeled, and nested.
Learn JSON syntax
JSON uses key-value pairs separated by commas. Objects are enclosed in curly braces, and arrays in square brackets. Keys must be in double quotes. For example: interface name GigabitEthernet0/1. This compact syntax is easy to read and parse.
Learn XML syntax
XML uses custom tags to define elements. Each piece of data is wrapped in an opening and closing tag, like interface name GigabitEthernet0/1. Attributes can provide additional metadata within the opening tag. XML is more verbose but highly structured.
Learn which protocol uses which format
NETCONF uses XML only. RESTCONF uses JSON or XML. Ansible and other automation tools can use either format depending on the module and device support. Knowing this mapping is critical for both exams and real-world configuration.
Practice reading payloads
Look at a YANG model and then read a JSON or XML payload that represents it. Identify the keys, values, nesting, and data types. This skill helps you verify that a payload matches the intended configuration before sending it to a device.
Understand validation and error handling
Devices validate incoming JSON or XML against the YANG model. If the payload is malformed or data types are wrong, the device returns an error. Knowing common errors helps you troubleshoot automation failures quickly.
Practical Mini-Lesson
Let us walk through a practical example of using JSON and XML in network automation. You are a network engineer at a mid-size company. You manage 20 Cisco Catalyst switches. You need to update the SNMP location string on all switches.
Manually doing this on each switch would take hours and risk human error. Instead, you write a Python script that uses the RESTCONF API. First, you identify the correct YANG model for the SNMP configuration.
You find that the model defines a leaf called snmp-location under the snmp-server container. Now you need to construct a JSON payload that sets this leaf to a new value. You write: snmp-server location Main Data Center.
Notice the structure: the key is snmp-server and inside it, location and its value. You wrap this in curly braces. You then use the requests library in Python to send an HTTP PATCH request to the RESTCONF endpoint of each switch.
The endpoint looks like https://192.168.1.1/restconf/data/Cisco-IOS-XE-native:native/snmp-server. The script iterates through all switches. For each one, if the request succeeds, you see a 204 No Content response.
If there is a syntax error in the JSON, you get a 400 Bad Request with an error message that explains the problem. You can then correct the JSON and retry. Now consider the same scenario using NETCONF.
Instead of RESTCONF, you use the ncclient Python library. You construct an XML payload that achieves the same goal. The XML payload would look like: config xmlns urnietfparamsxmlnsnetconfbase1.
0 snmp-server location Main Data Center snmp-server config. The XML is longer but equally functional. The key takeaway is that you must be fluent in the syntax of both formats. In professional practice, you will often rely on JSON for its brevity, but when you work with legacy systems or certain telecom equipment, XML is unavoidable.
Understanding both makes you a more versatile and effective automation engineer. Always validate your payloads using online tools or code libraries before sending them to production devices.
Memory Tip
For NETCONF, remember N for XML because XML has many Names. For RESTCONF, remember R for both formats because REST is Ready for anything.
Covered in These Exams
Related Glossary Terms
802.1Q is the networking standard that allows multiple virtual LANs (VLANs) to share a single physical network link by tagging Ethernet frames with VLAN identification information.
802.1X is a network access control standard that authenticates devices before they are allowed to connect to a wired or wireless network.
An A record is a DNS record that maps a domain name to the IPv4 address of the server hosting that domain.
Frequently Asked Questions
Do I need to memorize the exact syntax of JSON and XML for the ENCOR exam?
You need to be able to recognize and interpret basic syntax. You will not be asked to write a full payload from scratch, but you will need to identify syntax errors and understand which format a given snippet represents.
Is JSON replacing XML in networking?
JSON is more popular for new implementations, especially with RESTCONF and cloud APIs. However, XML is still widely used in NETCONF, legacy systems, and telecom. Both remain relevant for the foreseeable future.
Which protocol should I use for automation: NETCONF or RESTCONF?
RESTCONF is often preferred because it is easier to work with using HTTP and supports JSON and XML. NETCONF is more robust for transactional configuration changes and uses SSH, making it more secure in some environments.
What is a YANG model and how does it relate to JSON and XML?
A YANG model is a schema that defines valid configuration data for a network device. JSON and XML are the formats used to encode that data when sending it to the device via protocols like RESTCONF or NETCONF.
Can I mix JSON and XML in the same automation script?
You can, but you must use the appropriate protocol for each format. RESTCONF supports both. NETCONF only supports XML. So if you use NETCONF, you must use XML. If you use RESTCONF, you can choose either but stick with one per request.
What is the most common exam trap for JSON and XML?
The most common trap is assuming that NETCONF supports both JSON and XML. Many candidates see that RESTCONF supports both and incorrectly generalize. Remember the rule: NETCONF = XML only; RESTCONF = JSON and XML.
Summary
JSON and XML are the two primary data formats used in network automation, enabling structured communication between humans, scripts, and network devices. JSON is lightweight, using key-value pairs and curly braces, making it fast to parse and ideal for RESTCONF and modern APIs. XML is more verbose, using tags, and is required by NETCONF, which is widely used for robust, transactional configuration management.
Understanding the syntax, strengths, and protocol mappings of both formats is essential for passing the CCNP ENCOR exam and for performing real-world network automation tasks. The exam tests your ability to identify formats, compare their characteristics, and troubleshoot common errors. Common mistakes include confusing the syntax between the two formats and misremembering which protocol supports which format.
The best way to succeed is to practice reading and validating JSON and XML payloads, and to firmly associate NETCONF with XML and RESTCONF with both. Mastering these formats will not only help you pass the exam but also make you a more effective network engineer in an increasingly automated industry.