CCIE Routing and Switching (R&S) 400-101 V5.1 Written Exam: Identify Cisco Express Forwarding (CEF) Concepts

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CCIE Routing and Switching (R&S) 400-101 V5.1 Written Exam: Identify Cisco Express Forwarding (CEF) Concepts

In this article, I will be discussing Cisco CEF switching as part of Network Principles and Network Theory CCIE Routing and Switching (R&S) V5.1 exam blueprint topics.

Network Theory

  • Identify Cisco express forwarding concepts
    • RIB, FIB, LFIB, Adjacency table
    • Load balancing Hash
    • Polarization concept and avoidance

Let me summarize some of the key takeaways related to Cisco CEF switching as relevant to CCIE Routing and Switching (R&S) V5.1 exam blueprint topics.

Cisco Express Forwarding (CEF) Exam Essentials

  • Hardware based switching platforms use Content Addressable Memory (CAM) for storing the CEF related information.
  • The number of load balanced paths used is limited by the number of entries the routing protocol puts in the routing table, the default in IOS is 4 entries for most IP routing protocols with the exception of BGP, where it is one entry.
  • CEF polarization occurs when traffic uses per destination load balancing and the same algorithm is used throughout the network which causes traffic to not be load balanced after the first distribution.
  • RIB and LIB are control plane related tables, whereas FIB and LFIB are data plane
  • CEF adjacency and forwarding tables can be built independently
  • With BGP PIC enabled, CEF recursion is disabled when next-hop is learned via /32 mask or next-hop is directly connected

I sincerely hope that you found this video helpful. Please post your questions or suggestions in the comments and tell me how you are preparing for your CCIE Routing and Switching (R&S) V5.1 written and lab exams.

 

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