Full path validation

Would also be nice to have full path validation, currently the test only checks if at least one of the routers on the path implements ROV, not all of them.

Should be easy to implement, just set up a different endpoint with an invalid route, and a less specific valid route matching the prefix.

Locate the existing path validation test that currently checks whether at least one router on the path implements ROV. Start by running that test and tracing its endpoint and route setup. Add coverage using an invalid route with a less-specific valid route matching the prefix, and consider the work done when validation requires every router on the path to implement ROV.

Written by the indexing model from the issue text.