CCDE 400-007: Which BGP feature provides fast convergence?

Table of Contents

Question
Answer
Explanation
Reference

Question

Which BGP feature provides fast convergence?

A. BGP-LS
B. BGP FlowSpec
C. BGP-EVPN
D. BGP PIC

Answer

D. BGP PIC

Explanation

The correct answer to the question is D. BGP PIC (Prefix Independent Convergence).

BGP (Border Gateway Protocol) is an exterior gateway protocol used in large-scale networks to exchange routing information between different autonomous systems (AS). Convergence refers to the process of network devices reaching a consistent and stable state after a topology change or network event.

BGP PIC (Prefix Independent Convergence) is a feature that provides fast convergence in BGP networks. It aims to minimize the impact of link or node failures by reducing the time it takes for the network to recover and resume normal operation. Here’s a comprehensive explanation of BGP PIC:

Precomputed Backup Paths: BGP PIC utilizes precomputed backup paths, which are alternative paths to reach destinations in case of failures. These backup paths are precalculated and stored in the routing table before any failure occurs. By having backup paths readily available, BGP PIC significantly reduces the time required to reconverge the network after a failure.
Elimination of Recalculation: With precomputed backup paths, BGP PIC eliminates the need for the routers to recalculate alternative paths during the convergence process. This saves significant processing time and allows for faster recovery.
Fast Route Switching: BGP PIC enables fast route switching by allowing routers to switch to the precomputed backup paths immediately upon detecting a failure. This eliminates the need for routers to wait for the convergence process to complete before switching to backup paths, resulting in reduced downtime and faster recovery.
Scalability: BGP PIC provides scalability benefits by precomputing backup paths at the edge of the network, closer to the affected destination prefixes. This localizes the impact of failures and reduces the computational burden on core routers, enhancing overall network performance.

The other options listed in the question are not specifically designed to provide fast convergence:

BGP-LS (A) stands for BGP-Link State and is used to distribute link-state information within BGP networks. It focuses on collecting and distributing detailed network topology information rather than providing fast convergence.
BGP FlowSpec (B) is a feature that allows network operators to specify and distribute traffic filtering policies using BGP. It is primarily used for traffic engineering and policy enforcement, not for improving convergence speed.
BGP-EVPN (C) stands for Ethernet Virtual Private Network and is used for building overlay networks and providing services like VPNs over an IP/MPLS infrastructure. While BGP-EVPN provides scalability and flexibility in network design, it is not specifically designed to enhance convergence speed.

In summary, BGP PIC (Prefix Independent Convergence) is the BGP feature that provides fast convergence in BGP networks. It achieves this by utilizing precomputed backup paths, eliminating recalculation, enabling fast route switching, and enhancing scalability. BGP PIC significantly reduces the convergence time and minimizes the impact of failures, leading to improved network availability and reliability.

Reference

Cisco Certified Design Expert CCDE v3.0 400-007 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Cisco Certified Design Expert CCDE v3.0 400-007 exam and earn Cisco Certified Design Expert CCDE v3.0 400-007 certification.