Sorry for a basic question but...
When I'm viewing interface stats in something like MRTG, what determines receive vs transmit? On our external router interface, our ISP promises us 20MB "down" and 5MB "up".
So in MRTG that would mean my max should be 20MB receive and 5MB transmit?
First of all Megabits per second are correctly noted a Mbps or Mb, never as MB (Mega Bytes).
Second to answer your question, depends on which interface you measure. One facing ISP would work as you describe, one facing your LAN would have the figures inverted.