Interdomain routing enables each autonomous system (AS) to decide the routes toward any destination and exchange routing information with its neighboring ASs on the Internet. The Border Gateway Protocol (BGP), as the de facto routing protocol for interdomain routing, allows the administrators/operators to independently decide the routing policies for their ASs and each AS to select routes to destinations based on the locally determined routing policies. The Internet has evolved from a hierarchical and multi-tiered interconnection network to a meshed network, where ASs are interconnected with a dense topology and more and more potential paths can be used to reach a destination. Although each AS has the freedom to set up its routing policies, it is challenging to understand how a network’s routing policies might impact the resulting routing system. On one hand, the freedom in configuring local routing policies might jeopardize the safeness of the routing system. That is, configuring routing policies without constraints or coordination among ASs causes persistent interdomain routing oscillations on the Internet. On the other hand, these independently configured routing policies might not necessarily meet the intent of the network administrators/operators. Therefore, it is essential to ensure that the routing system is guaranteed to converge and to know whether the routing system satisfies the routing intent of network administrators/operators. This research aims to improve the understanding of the routing systems that are derived from the locally determined routing policies. To do that, three interesting topics are explored in this dissertation: (1) policy-rich interdomain routing through local coordination, (2) verifying inter-domain routing at Internet scale, (3) routing policy anonymization for verification.