Although there is an Exterior Gateway Protocol of the same name, EGP it has been superseded by BGP for a variety of reasons. IP addresses can be summarized to a single route Routing decisions within BGP can be based on CIDR 32 bit addresses and masks. A single, statically routed connection from a central site or an ISP to, for example, a remote office or home. BGP is not required in this configuration. A central site with at least two statically-defined or dynamically routed connections to remote locations.
Data only flows to and from the remote locations.
BGP is not required in this configuration. Each location is an autonomous system. BGP is required in this configuration. Another way to look at the requirement for BGP is if a customer has multiple locations with multiple routers, but does not want each location's routing tables to effect the others. This is the strategy used on the Internet to provide better reliability and higher performance.