> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/routing-units/untitled/define.md).

# define

The pointer to the routing unit definition file is a foreign key referencing [id](/io-docs/introduction-1/routing-units/untitled-1/id-rout_unit.def.md) in [**rout\_unit.def**](/io-docs/introduction-1/routing-units/untitled-1.md).