With more applications move to the Internet, scalability, both in time and space, has become one of the biggest concerns. There are two basic techniques for solving the scalability problem: hierarchy, such as the ones used in, and hashing, such as used in. Using hierarchy to achieve scalability has been well studied. But the application of hashing techniques in network area is still at the beginning stage. According to my knowledge, there is no previous survey discussing how to apply hashing techniques to solve problems in networking. In this paper, we give an in-depth survey on hashing techniques to networking systems. After we review the basic knowledge on hashing, we will address two important hashing techniques, bloom filter and consistent hashing. We envision these two techniques have more potential applications for us to find.