The Cisco DNA Center exhibit indicates a "BGP Flapping" issue, and the router output confirms that Bidirectional Forwarding Detection (BFD) is enabled for the BGP neighbor. BFD provides very fast failure detection, but if its timers are too aggressive for the underlying network conditions (e.g., minor jitter or packet loss), it can prematurely declare the neighbor down, causing the BGP session to flap.

The most appropriate solution is to make the BFD timers less aggressive. The command bfd interval 300 minrx 300 multiplier 5 on the relevant interface increases the BFD transmission/reception interval to 300 milliseconds and the dead timer multiplier to 5. This increases the total detection time, making the BFD session more resilient to transient network issues and stabilizing the BGP peering.

A: This command enables BFD, but the show command output confirms that BFD is already enabled for the neighbor.

B: This command modifies the BGP keepalive and hold timers. BFD operates independently and provides much faster detection, making these BGP timers irrelevant for failure detection when BFD is active.

C: This command disables BFD. While this would stop the BFD-induced flapping, it sacrifices the primary benefit of fast network convergence, which is generally not the preferred solution.

1. Cisco IOS XE Interface and Hardware Component Configuration Guide

Cisco IOS XE Gibraltar 16.12.x

"Configuring BFD Session Parameters on the Interface": This document details the bfd interval milliseconds minrx milliseconds multiplier number command. It explains that this command is used to customize BFD timers on an interface to prevent BFD from reporting false link failures on unstable networks. This directly supports the configuration in the correct answer. (Source: Cisco Official Documentation

URL: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproutebfd/configuration/16-12/irb-16-12-book/irb-bfd.html#ID-2112-0000004d)

2. Cisco IOS XE BGP Configuration Guide

Cisco IOS XE Fuji 16.9.x

"BGP Support for BFD": This guide explains that when BFD is enabled for a BGP neighbor using the neighbor fall-over bfd command

the BGP session state is tied to the BFD session state. If the BFD session goes down

BGP immediately tears down its peering relationship. This confirms why an unstable BFD session leads to BGP flapping. (Source: Cisco Official Documentation

URL: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproutebgp/configuration/xe-16-9/irg-xe-16-9-book/bgp-support-for-bfd.html)

3. Cisco SD-WAN BGP Configuration Guide

Cisco IOS XE SD-WAN Release 17.x

"Configure BFD for BGP": This document explicitly states

"If you configure BFD to be too aggressive

BFD may report a link as having failed

when the link has not failed. For example

if you configure a very low BFD timer and multiplier

a slight increase in traffic on a link may cause BFD to miss the required number of packets to keep the link active." This directly describes the problem scenario and validates the solution of adjusting BFD timers to be less aggressive. (Source: Cisco Official Documentation

URL: https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/routing/ios-xe-17/routing-book-xe/m-bgp.html#CiscoConcept.dita1109c59f-115e-411b-811b-111111111111)