N10-009 Question 143
Single answerDynamic routing: Border Gateway Protocol (BGP), Enhanced Interior Gateway Routing Protocol (EIGRP), Open Shortest Path First (OSPF)A company is merging with another organization and needs to exchange route information between the two companies' independently managed networks over redundant internet links. Internally, each company wants to keep using its own existing routing design, but the edge routers must support policy-based control over which public prefixes are advertised and accepted from the other company. Which routing protocol is the best choice for the edge routers in this scenario?
- A
BGP
- B
OSPF
- C
EIGRP
- D
RIP
Show answer and explanation
Correct answer: A
Explanation
The key requirement is interdomain routing between two independently managed networks while preserving each company's internal routing design. That points to an exterior gateway protocol rather than an interior gateway protocol. BGP is the industry-standard exterior gateway protocol used between autonomous systems and is specifically valued for policy control, route filtering, path selection, and scalable exchange of prefixes across organizational boundaries. OSPF and EIGRP are interior gateway protocols intended for use inside a single administrative domain, not as the primary protocol for exchanging routes between separate companies. This aligns with common enterprise and service-provider best practices and with vendor documentation from Cisco and standards documentation from the IETF for BGP-4.
- A. Correct.
Correct. Border Gateway Protocol (BGP) is designed for exchanging routing information between separate autonomous systems and supports granular policy-based routing decisions, prefix filtering, and route advertisement control. In a merger or multi-organization connectivity scenario where each side keeps independent internal routing, BGP is the standard choice at the network edge.
- B. Incorrect.
Incorrect. OSPF is a link-state interior gateway protocol intended for routing within a single administrative domain. While it scales well internally, it is not the preferred protocol for exchanging routes between separately managed organizations over internet-facing edge connections with policy-based control requirements.
- C. Incorrect.
Incorrect. EIGRP is an advanced distance-vector/hybrid interior gateway protocol primarily used within a single organization. Although it can handle internal route exchange efficiently, it is not the standard protocol for interdomain routing between separate autonomous systems with internet edge policy requirements.
- D. Incorrect.
Incorrect. RIP is an older distance-vector protocol with limited scalability and slow convergence compared with modern alternatives. It also lacks the robust interdomain policy controls required for exchanging routes between separate organizations.