Abstract: The campus network connected to two ISPs at the same time can achieve the purpose of sharing resources effectively.The key to achieving the purpose lies in a reasonable designing of the routing in routers connected with two ISPs.Based on a case study of the typical requirement of a campus network,this article makes a research on how to allocate flow and shift the IP to realize NAT through building ACL and strategic routing in boundary router.In addition,the paper illustrates the problem that the servers in campus network are unable to be visited because of the NAT and the inconsistent way of the input and outflow of data packages,and gives a solution to the problem.