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 <p...@tippete.net> wrote: > >>>>> "Mel" == Mel Beckman <m...@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 >