Linear camera movement

[DavidacrossAmerica]

I simply want to move a single node camera on the X axis across two keyframes. I've done this many times before without this issue, but when I do it now, the path is not linear as you see in this screenshot. I'm sure this is something simple, but I cannot find what to do about it. 

[Mylenium · Accepted solution]

Select the keyframes and right-click to check whether both temporal and spatial interpolation are set to linear.

Mylenium 

[DavidacrossAmerica]

Thanks. I knew it was something simple but couldn't find it. I just don't understand why the apparent default changed all of a sudden. But I know what to do now.