how far away did the philsophy of the classical greeks go? how far did east asian philsophy go? and what of the stuff in between, did they just interact with the people in their spheres or did they borrow ideas from outside too?
What do you define as eastern philosophy? The ancient greeks reached the edges of India and later (pre 1500) Islamic philosophers had real intellectual interactions with India (and the islamic world carried a version of the classical world within it's tradition).
for instance Al Biruni wrote a major work helping to introduce India to the wider Islamic world basic bio http://en.wikipedia.org/wiki/Abū_Rayḥān_al-Bīrūnī
Not really an expert on this but Peter Adamson talks a little bit about this in his podcast
http://www.historyofphilosophy.net/mughal notice the sources on every podcast page and feel free to leave a comment on his site asking the question since Peter Adamson (who is a professor) does a decent job at responding to queries.
hope this can kick off discussion and bring in people with more knowledge about this than i do (and you might try /r/askphilosophy