If you have a non European passport I would advise you to get a Eurail pass and, if challenged just show that passport. Then you can use the pass in an unlimited way in all countries without limits on your current country of residence.

If however you really want an Interrail pass then, again if challenged, you simply present your Schengen visa.

Thank you for your response.

My Passport is non EU passport. But I Have National Visa (Type D Schengen Visa). 

So, am I eligible for an Interrail pass?

READ above-you can in theory use both-but EUrail gives you better value as it is also unlimited valid In DE=Germany, where as InterRail only for the first trip OUT and last IN. That your passpt is from out of EU is blinding obvious if you need a visa.

If your passport is from a European country (Not just EU) then you need an Interrail pass with a 2 day limited use the country you declare in your application - national or temporary residence.

Otherwise you can choose between a Eurail pass (No restrictions in current temporary residential country, using your national passport) or an Interrail pass (restricted to 2 days in your temporary country of residence, using your visa if challenged.)