Strange behavior on the Juniper MX240

Mark Tinka mark at
Fri May 6 09:37:32 UTC 2022

On 5/6/22 11:26, Saku Ytti wrote:

> You are always here. You always need to understand your scale and how
> much resources you have available, what is possible and what is not.

Of course, if this was the case with the global Internet, we'd have far 
fewer problems making it work well than we do today :-).

> Existence or non-existence of configuration toggle to affect this
> doesn't make that situation worse or better.
> It is not implied to be a tactical short-term fix, it depends and you
> must understand what you are doing to determine your position in any
> case.

You and I (and many others) have enough experience to know that many 
operations will either underestimate or not understand the technical 
abilities (or disabilities) of their platforms, as long as it works, for 
the most part. Things like FIB programming and FIB scaling are some of 
the least understood and least monitored abilities of any platform, 
amongst others.

And yes, there are platforms where having or not having the hack enabled 
does make a material difference on either side of the pendulum 
(especially in platforms with a small FIB, to begin with).

My point is to remind the OP that if little care was given to this issue 
before it occurred, they should increase their focus on it going 
forward, not in spite of the re-carving hack, but also because of it.


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