Cisco IOS-XE Syntax Highlighting

Syntax highlighting for Cisco IOS and IOS XE configuration files in Visual Studio Code.

This extension is built around practical configuration review: important structures, values, and operationally significant commands should be easy to find without turning the entire configuration into visual noise.

Preview: Syntax coverage is actively being expanded. The extension is useful today, but it does not attempt to recognize every command or abbreviation supported by Cisco IOS and IOS XE.

Features

• Highlights common IOS and IOS XE configuration contexts and commands.
• Distinguishes interfaces, IP addresses, VLANs, routing processes, ACLs, AAA servers, and other frequently reviewed values.
• Makes operationally significant keywords stand out.
• Highlights Cisco ! comment lines.
• Highlights full-line Jinja2 comments ({# ... #}) commonly used in Ansible templates.
• Supports .ios, .iosxe, and .cisco files.

Highlighting colors are provided by your active VS Code theme. Because themes assign colors differently, the exact appearance may vary.

Example

Below configurations are generated by AI, and are not representative of production network configurations. However, highlighting is representative of VSCode Dark 2026 theme.

Routing Process configuration hightlighting:

AAA configuration highlighting:

Design approach

Cisco IOS accepts many abbreviated commands. This grammar intentionally focuses on canonical commands and a small number of common abbreviations rather than every syntactically valid shortening.

For example, IOS may accept all of the following:

int
inte
inter
interf
interfa
interfac
interface

This extension currently recognizes int and interface. This keeps the grammar understandable and reduces ambiguous matches.

Highlighting indicates that text is structurally or operationally significant; it does not validate whether a configuration is correct or safe.

Getting started

Open a file with one of the supported extensions:

router.ios
switch.iosxe
access-template.cisco

You can also assign the language manually from the language selector in the lower-right corner of VS Code by choosing Cisco IOS-XE.

For other filenames, add a VS Code file association:

"files.associations": {
    "*.cfg": "cisco-iosxe",
    "*.conf": "cisco-iosxe"
}

Current limitations

• Syntax coverage is incomplete and will grow incrementally.
• The grammar is a highlighter, not a parser, linter, formatter, or configuration validator.
• Most noncanonical command abbreviations are not recognized.
• Jinja2 support is currently limited to full-line comments.
• Some commands are context-sensitive in IOS but may be highlighted more broadly by this grammar.

Feedback and contributions

Bug reports, missing command examples, and focused improvements are welcome through the project's issue tracker. When reporting a highlighting problem, include a small sanitized configuration sample and describe which token should be highlighted differently.

Release history

See CHANGELOG.md for version history.

License

Released under the MIT License. See LICENSE.

Cisco, Cisco IOS, and Cisco IOS XE are trademarks of Cisco Systems, Inc. This independent project is not affiliated with or endorsed by Cisco Systems.