[c-nsp] Cisco IGP / BFD Dampening (Suppressing Unstable WAN Links)

[Antoine Monnier]

we had same kind of issue - we looked into BFD dampening but it did not do
what we needed - plus both end of a link need to support it.
Cisco SE said that they would feed back our experience to the BU - never
heard back though

One conversation on the topic.

https://supportforums.cisco.com/document/144626/bfd-support-cisco-asr9000

Definitely interested is someone has managed to solve that problem with BFD
dampening...without EEM scripts!


On Thu, Apr 27, 2017 at 6:52 AM, Troy Boutso <sensible115 at gmail.com> wrote:

> Hey all
>
> I have a fairly easy one for ya'll (I hope).
> I have a network consisting of multiple WAN Links which span all over the
> place. By WAN Links I am referring to private leased Layer 2 Circuits with
> Ethernet Hand offs.
>
> Each of our client sites has two of these types of links via alternate
> providers back to our 2 main "hub" sites.
>
> I am currently running. IS-IS (Level 2) with MPLS LDP and BFD for failure
> detections on every single link.
> iBGP (MP-BGP) is how I exchange all NLRI between sites... that all works
> perfect.
>
>
> I'll start off by saying 90% of the failures on my network involve one of
> these links going down due to some fibre cut or other carrier transmission
> issue. This is usually no big deal. As the BFD will detect the fault within
> about 2 seconds and traffic re-routes instantly. I usually see a few
> packets drop during this time. For what I do. This is completely
> acceptable.
>
> However yesterday I was thrown a curveball. Rather than a particular link
> simply going down. I saw it flap constantly for 2-5 minutes. Which is far
> worse than I've experienced in the past. In the past this has happened, but
> wasn't as bad (as in wasn't noticable for my customer). My model has stood
> up ... until now. I understand what happened. I just don't know the best
> way to address the issue and prevent it from being customer impacting.
>
>
> The flaps i am referring to are NOT link state events. Meaning the
> interfaces don't actually change state (the issue is somewhere in my
> provider's end). Therefore I don't think "ip dampening" would help. What I
> want is something at the BFD, ISIS level. To essentially poison/penalize or
> even disable forwarding over link in question for a certain amount of time.
> Until stability is maintained. And if the flapping persists, to continue
> applying the penalty... (hope you all get what I am saying here)
>
> I looked into "BFD Dampening" which is configured under a template. But is
> this really going to give me the desired result? Is there something else
> out there that I've overlooked?
>
> If BFD damping is correct. I've got questions about the values :)
>
>
> Kind Regards
> Troy
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