Which protocols do autonomous systems (AS) use to exchange routing information between themselves?

Autonomous Systems (AS) use Exterior Gateway Protocol (EGP) to exchange routing information between different systems. EGP is specifically designed for inter-domain routing, which is essential for communicating between distinct entities on the Internet. This is crucial for maintaining a cohesive routing structure, allowing AS to share routing information effectively across disparate networks.

In the context of routing protocols, EGP enables AS to communicate essential information such as the reachability of network prefixes, allowing for effective decision-making regarding the best paths for data transmission across the Internet. It establishes a framework where diverse AS can operate collaboratively, ensuring that data packets reach their destinations efficiently and reliably.

While Interior Gateway Protocols (IGPs), such as OSPF and other dynamic routing protocols, facilitate routing within a single AS, they are not suitable for inter-domain exchanges that are the hallmark of EGP, which focuses on interactions between different AS. This distinction is essential for understanding how global routing operates in the broader context of the Internet.