The Ramayana is considered older than the Mahabharata.
There are athentic descrition of North Eastern India in the Ramayana.
As you explained, its full of references in the Mahabharata.
Mamoni Raison, noted Assamese author, has boldly said, its the Ramayana and Mahabharata which binds NE with rest of India. Its true for rest of India too.
