The gateway was running on a linux box in a closet somewhere in the building so I was able to go there physically to resolve the issue.

With some foresight, one schedules a task to run a few minutes in the future to revert the change.

And one tests that revert by running it with a no-op change.

And one tests that the no-op change really is no-op by running it on a test system.

"Have you tried unplugging it and plugging it back in again?"