The core routers within a transit AS are running both IBGP and IGP. The edge routers within the transit AS are using the next-hop-self option to establish the IBGP sessions. What can be implemented…

Question

Options

• Aenable route redistribution from BGP into IGP
• Bdisable BGP synchronization on all the core routers
• Cenable CEF on all the core and edge routers
• Denable route redistribution from IGP into BGP
• Euse route reflectors within the core

• A
  8% (3)
• B
  3% (1)
• C
  86% (32)
• E
  3% (1)

Explanation

When edge routers use 'next-hop-self', core routers see the edge router's IP as the BGP next-hop for all external prefixes. Core routers must resolve this next-hop via IGP and then forward packets. Without CEF (Cisco Express Forwarding), each packet forwarding decision requires a CPU-based route table lookup, which is slow and does not scale. Enabling CEF on all core and edge routers enables hardware-assisted forwarding using the FIB (Forwarding Information Base) and adjacency table, dramatically improving throughput and reducing per-packet latency. A and D (redistributing between BGP and IGP) introduce routing instability risks and are not performance improvements. B (disabling synchronization) is irrelevant since synchronization is already disabled by default in modern IOS. E (route reflectors) addresses IBGP scalability, not forwarding performance.

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