How do you travel from Scotland to Northern Ireland or vice versa?

Orginally was just going to Scotland. Fly to Edinburgh, rent a car and drive around to other areas. Then, DH suggested we go to Belfast as well. How can this be done?

I was thinking of flying open jaw from/to these cities (Continental has nonstop from Newark) and I found a ferry to take. Problem seems to be the price of a car rental to rent in one and drop in the other.

Any ideas?

Don't take the ferry - way too much time and hassle. You can fly from Edinburgh to Dublin on Ryanair or Aer Lingus, or Edinburgh to Belfast on EasyJet. There may be others I don't know about. The only thing you need to watch out for is the weight limits and extra fees, particularly with Ryanair. Just make sure you read the fine print.

Ferries from Stranraer or Larne. But as jent says only take them if it fits your plans. Otherwise use a cheap carrier to fly

It didn't click till now that you might not be near Edinburgh when you're ready to go to NI. You can also fly from Glasgow to Belfast on Ryanair or Easyjet.

I think you rent a car in Scotland, leave it there and rent another in Ireland, ferries are used by people who want to take their own car.

The ferry is only 2 hours between Belfast and Stranraer. It is a high speed Stena Line that really moves. It is a nice ship.

The problem is the local sloooow trains between Stranraer and Glasgow, over 4 hours. Then it's another hour to Edinburgh on a good train.

Maybe you can drop the car in Stranraer? Or, since Edinburgh and Belfast are both in the UK, there might be a reasonable drop off charge.