[Xorp-users] route flap damping triggers on eBGP duplicate updates?

Jonathan Park jpark at cs.ucla.edu
Sat May 9 13:05:04 PDT 2009


Thanks Bruce for the reply.

On Sat, 2009-05-09 at 19:50 +0100, Bruce Simpson wrote:
> Hi Jonathan,
> 
> Have you actually observed this happening, or is this purely an 
> observation based on code inspection?
> 

It was based on code inspection.  Duplicating this needed some
non-trivial test setup (requiring me to replay duplicate bgp updates).
So I looked at the code, and it looked like it is giving the penalty.
I was just wondering if someone already looked into this or what was the
initial design.


> Jonathan Park wrote:
> > Hi Xorp users,
> >
> > I was looking at XORP code and found that route flap damping can be
> > triggered by eBGP duplicate updates (i.e. all attributes are the same),
> > giving them the same penalty value of 1000.
> >
> > Is that true?  If so, is it done intentionally?
> >   
> 
> It would be really helpful, when reporting this sort of problem on the 
> list, if you could illustrate the call graph(s) involved.
> I find KScope is an excellent tool for doing this sort of work; it can 
> export call graphs via GraphViz, I believe there may be text export for 
> call trees in 1 direction also.
> 
> So, 1000 is the FIXED value in damping.cc. Other than that, I haven't 
> had time to read into this further. Can you elaborate further on how you 
> believe this condition is being triggered?
> 

I think I will do what you suggested and will get back to you with more
details.

Thanks,

Jonathan


> thanks,
> BMS



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