[195113] in North American Network Operators' Group
Re: Long AS Path
daemon@ATHENA.MIT.EDU (jim deleskie)
Thu Jun 22 08:47:25 2017
X-Original-To: nanog@nanog.org
In-Reply-To: <874lv8zh7e.fsf@snoopy.tippete.net>
From: jim deleskie <deleskie@gmail.com>
Date: Thu, 22 Jun 2017 09:47:20 -0300
To: Pierfrancesco Caci <pf@tippete.net>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
I see 5+ prepends as maybe not reason to have your "BGP driving license
revoked" but if I can continue with the concept that you have your BGP
learners permit.
If I think back to when I learned to code or when making ACL's, we still
used line number and practice would be to give ourselves lots
of space 5 or 10 numbers in case we have to insert something in the middle.
ie I need 2 sets of prepends, I'm still learning this stuff
so I'll go with 5 and 10. We all started somewhere, we all did dumb stuff,
hopefully, we all learned.
12AS hops, I have to go see how they are connected now, maybe someone in
that chain needs to be invited by an IX to a NANOG or GPF or some such,
that can't be super efficient.
-jim
On Thu, Jun 22, 2017 at 3:09 AM, Pierfrancesco Caci <pf@tippete.net> wrote:
> >>>>> "Mel" == Mel Beckman <mel@beckman.org> writes:
>
>
> Mel> Why not ask the operator why they are pretending this path?
> Perhaps
> Mel> they have a good explanation that you haven't thought of. Blindly
> Mel> limiting otherwise legal path lengths is not a defensible
> practice, in
> Mel> my opinion.
>
> Mel> -mel beckman
>
>
> A prepend like that is usually the result of someone using the IOS
> syntax on a XR or Junos router.
>
> Long ago, someone accidentally prepending 255 times hit a bug (or was it
> a too strict bgp implementation? I don't remember) resulting in several
> networks across the globe dropping neighbors. One has to protect against
> these things somehow.
>
> As a data point, here is how many prefixes I see on my network for each
> as-path length, after removing prepends:
>
>
> aspath length count
> -------------------------
> 0: 340
> 1: 47522
> 2: 292879
> 3: 227822
> 4: 58390
> 5: 10217
> 6: 2123
> 7: 638
> 8: 48
> 9: 58
> 11: 20
> 12: 2
>
>
> So, does your customer have a legitimate reason to prepend more than 5
> times? Maybe. I still think that anyone that does should have their BGP
> driving licence revoked, though.
>
> Pf
>
>
>
>
> --
> Pierfrancesco Caci, ik5pvx
>
