[j-nsp] BFD/IS-IS wait to re-establish adjacency after failure tweak knob?

[Adam Vitkovsky]

> Clarke Morledge
> Sent: Wednesday, May 18, 2016 11:54 PM
>
> I am trying to figure out the best way to configure an MX router, on an
> interface, to wait a specific time before it can re-establish an IS-IS adjacency,
> after an adjacency has been lost.
>
> Assume I am using BFD with reasonably short timers/multipliers to detect
> when an IS-IS adjacency fails, without changing the default IS-IS timers.
> I have a situation where a point-to-point link, with an L2 device in between, is
> sometimes losing the adjacency, as desired, due to BFD timers/mulipliers
> downing a session.
>
> However, the IS-IS adjacency is coming up more quickly than desired. On
> average, it is coming up 7-8 seconds later. Unfortunately, the L2 link is still
> unstable, so the BFD causes the session to drop again fairly quickly. This
> causes a lot of flapping that I do not need.
>
> What is the appropriate JUNOS tweak knob to force IS-IS to wait a longer
> time on the unstable link, before trying to establish the adjacency?
>
I see what you mean I'm afraid there's no "ISIS adjacency dampening" feature.
And unfortunately there's no support to register the BFD session directly with physical link or IFL to monitor it's state.
Another option would be to use event options and disabling and enabling the interface manually, but once again I see there's no support for BFD (maybe in your version of code there will be).
So I guess what you remain with is LFM link-fault-management (you can use sub second timers there) to put the interface to a rest and use "hold-time up" to introduce a desired delay getting it up again.

/rant/
I don’t understand why BFD can't be configured as a standalone protocol under protocols stanza same way as oam lfm is.
Something like the below.
set protocols bfd interface ae0 pdu-interval 100
set protocols bfd interface ae0 pdu-threshold 3
set protocols bfd interface ae0 apply-action-profile put-link-to-a-rest
set protocols bfd action-profile put-link-to-a-rest event link-adjacency-loss
set protocols bfd action-profile put-link-to-a-rest action link-down
/rant/


adam











        Adam Vitkovsky
        IP Engineer

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