You don't have to wonder. You can call and ask them. -mel via cell
On Jun 22, 2017, at 5:47 AM, jim deleskie <deleskie@gmail.com> wrote:
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