Routable data on Garmin Dakota 20?

It would help if you specified which website you downloaded the OSM Garmin maps from - some support routing, others don't.

Also, how the Garmin map format works with address searching in the is not fully understood. So it is not properly supported by Mkgmap, the software used to generate most OSM based Garmin maps. So this means searching for an address doesn't work on some Garmin devices.

But there are others ways of choosing a location to route to. ie you can choose "Find", then cities (or shops, hotels, or some other sort of POI), then select a place from the list. Or you can scroll around the map, and select a point. Then if you choose "go to", the Garmin will generate a route to that location, including directions of where to turn.

So routing probably does work, its just address searching that might not.

I too have a Dakota 20 and also had the same issue. AFAICT, OSM doesn't embed the province, street, postcode etc. data that's required and you'll only get that functionality with commercial products such as Garmin's City Navigator.

However, if you create a waypoint at your required destination and the OSM-based map set you have loaded provides routing, the Dakota 20 can guide you to that destination. You will need to set the routing mode to car/motorcycle, bicycle, etc. as appropriate. Also, if your default routing mode is "offroad", you'll need to select Navigation->Reroute on road. You don't get spoken instructions - just beeps at each turn with a purple route marked and an arrow to indicate which road to take.

Maps from http://www.raumbezug.eu/ag/internet/osmGarmin.htm seem to be routable (at least on the level of streets) on garmin dakota 20.