What Is the BFD Multiplier in Application-Aware Routing?

300-415 By islever Editorial Last updated

Short answer

A In application-aware routing the BFD multiplier defaults to 6, so the last six poll intervals drive the tunnel's SLA loss, latency and jitter classification.

Question

What is the BFD multiplier in application-aware routing?
  1. 6 Correct Answer
  2. 7
  3. 8
  4. 9

Key Takeaways

The question tests the AAR SLA-classification multiplier (default 6), not the tunnel-liveness BFD multiplier (default 7) that most candidates memorize first.

In Cisco SD-WAN application-aware routing (AAR), the BFD multiplier sets how many poll intervals are averaged to compute mean loss, latency and jitter, and its default value is 6. This page establishes that option A is correct and explains why the familiar tunnel BFD multiplier of 7 does not answer this question.

Common mistake: Picking 7 because it is the widely cited default BFD multiplier for SD-WAN tunnel liveness (hello-interval 1000 ms, multiplier 7, DSCP 48) — but the AAR multiplier that averages poll intervals for SLA classification defaults to 6.

Expert Analysis

Why the Answer Is Correct

In Cisco SD-WAN application-aware routing, each tunnel carries BFD probes whose poll intervals capture loss, latency and jitter. AAR then classifies the tunnel's SLA using the last N poll intervals, where N is the BFD multiplier — a user-configurable parameter in the AAR profile. The Cisco default for that multiplier is 6, so the SLA verdict is derived from the six most recent poll intervals. Option A (6) is therefore the correct value. This matches what iking describes on the page: "The default value for the BFD multiplier in application-aware routing is 6."

Why the Other Options Are Wrong

Option B (7) is the real-world trap: it is the default BFD multiplier for tunnel liveness on Cisco SD-WAN devices, cited alongside hello-interval 1000 ms and DSCP 48, but it is not the AAR SLA multiplier. As jstaruch put it, "with AAR it is different from the default BFD multiplier by normal SDWAN tunnel," and Networkchamp87's own quote about probes being lost before a tunnel is declared down describes liveness detection, not SLA averaging. Options C (8) and D (9) are pure distractors — neither value is a Cisco default for any SD-WAN BFD multiplier, and no commenter or Cisco document endorses them.

Community Comment Notes

The anonymous vote distribution (70 for A, 30 for B) is not proof on its own, but it aligns with the AAR documentation: the 6-multiplier value is the one exposed in the vManage AAR profile and reflected in the SLA-classification explanation that "the information from all the poll intervals (specifically, from the last six poll intervals) is used to determine the classification." The B-voters, including hamidreza0010 and Stanleymahamadi's later reply, are repeating the generic SD-WAN BFD liveness values rather than the AAR multiplier. Read the question's qualifier carefully — "in application-aware routing" is doing all the work here.

Official Reference

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/command/iosxe/qualified-cli-command-reference-guide/m-bfd-commands.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

Anchor on the qualifier phrase: if the stem says "application-aware routing," think SLA classification and the default multiplier of 6; if it says tunnel, liveness or hello-interval, think the multiplier of 7. Memorize the pair (AAR = 6 for poll-interval averaging, tunnel BFD = 7 for declaring a tunnel down) so the distractor cannot flip your answer.

Frequently Asked Questions

Why is the AAR BFD multiplier 6 and not 7?

Six is the default multiplier that averages the last six poll intervals for AAR SLA classification; seven is the separate default multiplier used for tunnel liveness detection.

What does the AAR multiplier actually control?

It multiplies the poll interval to define how far back AAR looks when calculating mean loss, mean latency and mean jitter for the tunnel.

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Community Votes

A
70%
B
30%

70% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 8 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 8

  1. iking 👍 3 Answered A
    A. 6 The BFD multiplier in application-aware routing is a user-configurable parameter that determines the time to calculate mean loss, mean latency, and mean jitter. This value multiplies the polling interval to specify the time for these calculations. The default value for the BFD multiplier in application-aware routing is 6.
  2. [Removed] 👍 2 Answered A
    To determine the SLA classification of a tunnel, application-aware routing uses the loss, latency, and jitter information from the latest poll intervals. The number of poll intervals used is determined by a multiplier. By default, the multiplier is 6, so the information from all the poll intervals (specifically, from the last six poll intervals) is used to determine the classification. Reference: https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/policies/ios-xe-17/policies-book-xe/application-aware-routing.html
  3. Raynecore 👍 2 Answered A
    https://www.cisco.com/c/en/us/td/docs/routers/sdwan/command/iosxe/qualified-cli-command-reference-guide/m-bfd-commands.html
  4. Networkchamp87 👍 1 Answered B
    The Multiplier value determines how many consecutive BFD probes must be lost before a vEdge router declares a tunnel as down, as illustrated in figure 3 below. The BFD default values in Cisco SD-WAN are hello-interval 1000msec, multiplier 7, and dscp value of 48 . https://www.networkacademy.io/ccie-enterprise/sdwan/application-aware-routing-app-route-policy#:~:text=The%20Multiplier%20value%20determines%20how,illustrated%20in%20figure%203%20below.&text=The%20BFD%20default%20values%20in,and%20dscp%20value%20of%2048%20.
  5. jstaruch 👍 1 Answered B
    It looks that with AAR it is different from the default BFD multiplier by normal SDWAN tunnel ... The BFD default values in Cisco SD-WAN are hello-interval 1000msec, multiplier 7, and dscp value of 48 https://ccieme.wordpress.com/2021/02/08/sd-wan-application-aware-routing/ https://www.networkacademy.io/ccie-enterprise/sdwan/application-aware-routing-app-route-policy
Show 3 more comments
  1. hamidreza0010 👍 1 Answered B
    correct answer is B
  2. Stanleymahamadi 👍 1
    correct A
  3. Stanleymahamadi 👍 1
    B correct

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