Voice over IP technology integrates data and voice networks and offers flexibility by supplying device interoperability using standards-based protocols. Routing is an essential data networking function that provides an efficient real-time data delivery VoIP requires. Best effort networks leverage Interior Gateway Protocol technologies to determine paths for routing packets between hosts. Architects for best-effort networks provide services by over-provisioning the links and routers so that network congestion does not introduce unwanted levels of latency, jitter, and packet loss. Route re-convergence can be detrimental to VoIP users in the middle of a conversation, as it impacts both latency and jitter. This paper studies how VoIP performance can be affected by different routing behaviors which include Routing Information Protocol, Open Shortest Path First and Enhanced Interior Gateway Routing Protocol. Network modeling and simulation have been carried out with OPNET Modeler to evaluate and compare performances.