On Fri, Jul 12, 2024 at 07:34:28AM +0000, Ponikierski, Grzegorz wrote: > It assumes that Extended Length bit of Attribute Type is properly implemented > so community attribute can use attribute length field as 2 octet field, right?
Yes, that is a standard part of BGP. > How situation changes with RFC 8654<http://www.rfc-editor.org/info/rfc8654> - > Extended Message Support for BGP? With that enabled on both sides, there is still 1 kB reserved for prefixes, so you can have 63 kB for attributes, i.e. ~16128 standard, ~8064 extended, or ~5376 large communities. But propagation of such route will break on the first non-RFC8654 session. > On Fri, Jul 12, 2024 at 02:30:10AM +0000, Ponikierski, Grzegorz via > Bird-users wrote: > Hello all! > > How many standard communities, extended communities and large > communities, user can apply on a route using Bird? BGP UPDATE message has > finite size so I guess that there must be a limit somewhere. > > Hello > > There is no specific limit on communities, just a limit on overall BGP > attribute length on export, which is 1 kB less than BGP message size > (there is 1 kB reserved for prefixes). So with regular BGP messages, > there can be at most 3 kB of attributes, which is ~768 standard, ~384 > extended, or ~256 large communities. In fact, it is a slightly less due > to attribute framing and presence of other attributes than communities. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@crfreenet.org) "To err is human -- to blame it on a computer is even more so."
