I am booking an Addis to Djibouti flight that stops in DIR (other airport in Ethipia), and am confused as to how this works from an immigration standpoint...

I assume as we board in Addis, some passengers will be headed to Djibouti )INternational Flight) and some to DIR (Domestic)... Also, assume some passengers will be boarding in DIR for the final leg to DJI (Internation flight).

My question, is how does this work logistically in Addis when we board? Do DOmestic and International passengers board together at Addis? (And the crew checks the boarding pass to let passengers off at DIR)?