In this paper we will present the results of two DTN demonstration activities carried out in the ESA Ground Segment. The first demonstration has been prepared with the OPS-SAT spacecraft, to demonstrate a full DTN protocol stack with CFDP, Bundle Protocol, LTP, CCSDS Space Packet Protocol and show the ESA Ground Segment Bundle Protocol implementation capabilities. The second demonstration has been performed in collaboration with Morehead State University, NASA JPL and D3TN, with the aim to show interoperability of DTN implementations across space agencies and external partners.