Which of these is a reason to carry routes that originate outside your network in an EGP, such as BGP, rather than in your IGP, such as OSPF, EIGRP, or IS-IS?

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B. to prevent failures outside your network from impacting your internal network operation IGPs such as OSPF, EIGRP, and IS-IS are designed for fast intra-domain convergence and are sensitive to topology changes - redistributing hundreds of thousands of external prefixes into an IGP would cause every external BGP flap or route withdrawal to trigger a full SPF or DUAL recalculation inside the network. BGP is specifically designed to carry large numbers of external routes with features like route dampening that absorb external instability, isolating the internal domain from the volatility of the global routing table.

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A. to provide better control over the distribution of the default route inside your network Default route distribution inside the network is an IGP policy function and is not a reason to keep external routes in BGP rather than the IGP.

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C. to provide faster convergence to destinations outside your network BGP convergence is slower than IGP convergence because BGP uses TCP-based sessions with configurable timers (keepalive, hold-down), so faster convergence is the opposite of what BGP provides.

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D. to provide a growth path for the core of your network Carrying external routes in BGP does not provide a growth path for the internal network core - core scaling is addressed through IGP design, hardware upgrades, and route summarization.

Which of these is a reason to carry routes that originate outside your network in an EGP, such as BGP, rather than in your IGP, such as OSPF, EIGRP, or IS-IS?

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