In v4, most of the operators filter BGP updates for prefixes longer than a /24, to preserve the size of the full view.

What about IPv6 ? Is there such "convention" that stands out ?

1 Answer 1


These days it's usually at /48, and it's very unlikely to ever be longer.

There are still AS' filtering longer than /32 though, but they should all have a default at this point (Verizon were a hold-out, but I believe they've given up).

There are also AS' filtering on allocation lengths, so if you got a /32 they might require you advertise it as such (based on the various RIR's documented allocation policies).

  • 1
    Wow, filtering on allocation length ? That makes impossible for a content provider to serve geo-based prefixes, right ? Commented May 18, 2013 at 11:19
  • 1
    Not really, if they're disparate networks the RIR's allow multiple allocations in the correct space (at least ARIN, RIPE & APNIC do). There was a recent NANOG thread about this.
    – LapTop006
    Commented May 18, 2013 at 11:22
  • 1
    I should really subscribe to NANOG then, even if I'm french ! Commented May 18, 2013 at 11:28
  • It's as close to a global NOG as it gets, although posting non-North American content usually gets complaints.
    – LapTop006
    Commented May 18, 2013 at 11:35
  • @BenjaminA.: This has been discussed on FRnOG too. See mail-archive.com/[email protected]/msg22235.html
    – petrus
    Commented May 19, 2013 at 9:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.