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Difficulty: MediumRouting Concepts and Dynamic Routing Protocols

An enterprise network administrator is deploying a new edge connection to an external Internet Service Provider (ISP) to exchange public routing information across autonomous boundaries. The internal network currently uses OSPF for internal routing. Which routing protocol should be deployed on the edge router facing the ISP, and what is the primary reason for this selection?

  1. Border Gateway Protocol (BGP), because it is an Exterior Gateway Protocol (EGP) designed to route traffic between different Autonomous Systems across the Internet.Answer
  2. B
    Open Shortest Path First (OSPF), because extending the internal link-state protocol to the ISP eliminates administrative distance recalculation overhead.
  3. C
    Routing Information Protocol version 2 (RIPv2), because its distance-vector hop-count metric minimizes memory requirements on edge routers receiving Internet routes.
  4. D
    Static routing with Default Gateway ARP, because Layer 3 routers rely on address resolution broadcasts to dynamically learn ISP peer routes.

Answer

Border Gateway Protocol (BGP) should be deployed because it is an Exterior Gateway Protocol (EGP) specifically designed to handle routing between different Autonomous Systems across public network boundaries.
Border Gateway Protocol (BGP) is the standard Exterior Gateway Protocol (EGP) used across the global Internet to exchange routing information between separate Autonomous Systems (ASes). It allows enterprise edge routers to establish peering sessions with ISPs and exchange policy-based routing information.

Step-by-Step Solution

1
Analyze the network requirement boundary.
The scenario specifies connecting an internal enterprise network to an external ISP across an autonomous boundary.
Routing within an organization requires an Interior Gateway Protocol (IGP), while routing between independent organizations/ISPs requires an Exterior Gateway Protocol (EGP).
2
Evaluate protocol classification options.
OSPF and RIPv2 are Interior Gateway Protocols (IGPs). BGP is the standard Exterior Gateway Protocol (EGP).
BGP uses Autonomous System numbers (ASNs) and path-vector metrics to manage policies and routes between distinct ISP networks.
3
Select the correct dynamic routing protocol for the ISP edge.
Border Gateway Protocol (BGP) is selected.
Only BGP meets the operational requirements for inter-Autonomous System path vector routing and policy control on the public Internet edge.

Key Concept

Interior vs. Exterior Gateway Protocols (IGP vs. EGP)
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Topics

Routing Concepts and Dynamic Routing Protocols

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