Re: Question about normal ops - BGP Flaps nightly

[Christopher Morrow <morrowc.lists () gmail com>]

On Fri, Nov 22, 2019 at 12:32 PM Baldur Norddahl
<baldur.norddahl () gmail com> wrote:
> On Fri, Nov 22, 2019 at 1:21 AM Christopher Morrow <morrowc.lists () gmail com> wrote:
> > On Fri, Nov 22, 2019 at 2:01 AM Saku Ytti <saku () ytti fi> wrote:
> > > On Thu, 21 Nov 2019 at 19:44, Baldur Norddahl <baldur.norddahl () gmail com> wrote:
> > >
> > > > A BGP reset can cause routing trouble for as much as 15 minutes. Since you have two sessions that mitigates the 
> > > > problem somewhat. But nevertheless this will not be acceptable.
> > >
> > > As there are best path algorithms which consider route age, BGP reset
> > > impact may be indefinite.
> >
> > fortunately we have a second actual provider... so this all isn't
> > super impacting to us, just weird and unexpected on my part.
>
> No that is not helping. When the BGP session flaps your routes via that provider are withdrawn. Everyone out there 
> that were using those routes will need to switch. But consider the following:
>
> ISP A has routes from both of your providers
> ISP B has A as uplink
>
> BGP works so that ISP A is only announcing the route that he is actually using to ISP B. ISP B therefore does not 
> have both of your routes. When the active route is withdrawn ISP B will momentary be without any route to your 
> network. It can take some time after the withdraw before ISP A announces that he now is using the alternative route. 
> This gets worse with longer chains. Also some ISPs are using route flap limiting techniques that can prolong this 
> process.
>
> As I said, my experience is that you can expect as much as 15 minutes of flaky internet after a BGP reset. This is 
> with multiple transit providers.

Yup, I'm sensitive to flapping causing problems. This was why i
started the thread, which really should have been:
  "Is there a well known bug people are working around? or is this a
new problem I should chase with the provider? or 'nah, everyone does
this, you just aren't normally paying attention'"

> I can not say too much about why you have BGP resets, but I can say that you really want it fixed. It will affect 
> your connectivity.

fortunately 3am local time is not prime-internet-use time :) phew!
(not a great excuse though, of course)

I'll be chasing up the provider to see what's up.
thanks!
-chris

> Regards,
>
> Baldur