Which protocol routes traffic between different autonomous systems?

Which protocol routes traffic between different autonomous systems?

• A. NAT Network Address Translation
• B. IGP Interior Gateway Protocol
• C. EGP Exterior Gateway Protocol
• D. BGP Border Gateway Protocol

Answer: (C)

Routing between different autonomous systems is about interdomain routing, where different networks must share reachability information to forward traffic across the internet. The protocol designed for this job is Border Gateway Protocol. It operates between ASes, using TCP for a reliable connection, and it makes path decisions based on attributes like AS_PATH, next-hop, and various policy rules that administrators set. This combination lets networks control routing policies and avoid loops while selecting the best path to a destination across multiple autonomous systems. Historically, Exterior Gateway Protocols like EGP handled inter-AS routing, but they’re largely obsolete today due to limitations in scalability and policy control. NAT and Interior Gateway Protocols serve different purposes—NAT translates addresses, and IGPs route inside a single AS. So the protocol that routes traffic between autonomous systems is BGP.

Routing between different autonomous systems is about interdomain routing, where different networks must share reachability information to forward traffic across the internet. The protocol designed for this job is Border Gateway Protocol. It operates between ASes, using TCP for a reliable connection, and it makes path decisions based on attributes like AS_PATH, next-hop, and various policy rules that administrators set. This combination lets networks control routing policies and avoid loops while selecting the best path to a destination across multiple autonomous systems. Historically, Exterior Gateway Protocols like EGP handled inter-AS routing, but they’re largely obsolete today due to limitations in scalability and policy control. NAT and Interior Gateway Protocols serve different purposes—NAT translates addresses, and IGPs route inside a single AS. So the protocol that routes traffic between autonomous systems is BGP.