Do I need to plug internal cable routing ports? I have just ordered a OneUp Components 42T sprocket and a Race Face 30T Narrow/Wide single ring so that I can convert my 3x10 drive train into a 1x10.  This means that I'll be removing the front derailleur all together.  I have a carbon frame with internal cable routing so once I've removed the shifter cable there will be open "ports" in the frame.  Is it important to plug these ports?  What might happen if I don't plug them?  There is one where the cable enters at the top of the frame, and one under the bottom bracket where the cable exits.
I would plug them. If left open you will have the chance of water ,dirt, etc, inside the frame. The water and grit will eventually make its way to the bottom bracket. Even if the bearings are sealed it will still get on the threads of the bearing shell or threaded inset potentially making it difficult to remove.