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400-007 · Question #315

Enterprise XYZ wants to implement fast convergence on their network and optimize timers for OSPF. However, they also want to prevent excess flooding of LSAs if there is a constantly flapping link on…

The correct answer is D. OSPF throttling timers. OSPF throttling timers control the rate at which LSAs are generated and re-originated, directly preventing LSA flooding storms caused by a flapping link. This is the correct mechanism for dampening excessive LSA generation.

Designing Network Infrastructure

Question

Enterprise XYZ wants to implement fast convergence on their network and optimize timers for OSPF. However, they also want to prevent excess flooding of LSAs if there is a constantly flapping link on the network. Which timers can help prevent excess flooding of LSAs for OSPF?

Options

  • AOSPF flooding timers
  • BOSPF delay timers
  • COSPF propagation timers
  • DOSPF throttling timers

How the community answered

(22 responses)
  • A
    5% (1)
  • C
    9% (2)
  • D
    86% (19)

Why each option

OSPF throttling timers control the rate at which LSAs are generated and re-originated, directly preventing LSA flooding storms caused by a flapping link. This is the correct mechanism for dampening excessive LSA generation.

AOSPF flooding timers

OSPF flooding timers is not a recognized standard OSPF timer category in Cisco IOS; there is no such configurable parameter for rate-limiting LSA propagation.

BOSPF delay timers

OSPF delay timers is not a standard Cisco IOS OSPF timer construct; it does not map to any configurable feature that suppresses LSA generation.

COSPF propagation timers

OSPF propagation timers is not a valid Cisco IOS OSPF timer type and does not correspond to any documented mechanism for controlling LSA flooding behavior.

DOSPF throttling timersCorrect

Cisco IOS OSPF throttle timers (configured via 'timers throttle lsa') implement an exponential back-off algorithm that increases the delay between successive LSA originations for the same LSA, so a continuously flapping link produces progressively fewer LSAs rather than flooding the network at full rate.

Concept tested: OSPF LSA throttle timers for flap dampening

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/xe-16/iro-xe-16-book/iro-timers-pacing.html

Topics

#OSPF#throttling timers#LSA flooding#fast convergence

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