how to design OSPF convergence

Latest reply: Dec 24, 2018 09:14:06 204 6 10 0

Regarding the fast convergence design of OSPF, we can control it by setting an intelligent timer.

On an unstable network, routes are calculated frequently, which consumes a great number of CPU resources. In addition, LSPs that describe the unstable topology are generated and transmitted on the unstable network. Frequently processing such LSAs affects the rapid and stable operation of the entire network.

To speed up route convergence on the entire network, the OSPF intelligent timer controls route calculation, LSA generation, and LSA receiving.

The OSPF intelligent timer works as follows:

l  On a network where routes are calculated repeatedly, the OSPF intelligent timer dynamically adjusts the route calculation based on user's configuration and the exponential backoff technology. The number of route calculation times and the CPU resource consumption are decreased. Routes are calculated after the network topology stabilizes.

l  On an unstable network, if a router generates or receives LSAs due to frequent topology changes, the OSPF intelligent timer can dynamically adjust the interval. No LSAs are generated or processed within an interval, which prevents invalid LSAs from being generated and advertised on the entire network.

The parameter of the timer is as below:

Table 1-1 OOB OSPF Fast Convergence Parameter Design

OSPF Fast convergence

Intelligent timer for receiving   LSAs

The maximum delay is 100 ms.   The first delay is 50 ms, and the incremental delay between two LSA reception   attempts is 50 ms. The receiving interval must be less than or equal to the   update interval.

Intelligent timer for updating   LSAs

The maximum delay is 500 ms.   The first delay is 50 ms, and the incremental delay between two LSA update   attempts is 100 ms.

SPF intelligent timer

The maximum delay is 200 ms.   The first delay is 50 ms, and the incremental delay between two SPF   calculations is 50 ms.


The configuration template is as below:

Table 1-2 OOB OSPF fast convergence configuration


ospf 1

spf-schedule-interval intelligent-timer 200 50 50

lsa-originate-interval intelligent-timer 500 50 100

lsa-arrival-interval intelligent-timer 100 50 50


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Created Dec 22, 2018 16:29:50 Helpful(0) Helpful(0)

That's what I need
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Created Dec 22, 2018 16:30:02 Helpful(0) Helpful(0)

It is very helpful for the learner in the first stage.
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Created Dec 22, 2018 17:23:39 Helpful(0) Helpful(0)

are these parameters associated with each other?
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Created Dec 22, 2018 17:38:17 Helpful(0) Helpful(0)

Willing to learn more
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MVE Created Dec 23, 2018 01:46:42 Helpful(0) Helpful(0)

Detailed explanation.
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Created Dec 24, 2018 09:14:06 Helpful(0) Helpful(0)

  • x
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