On 02/10/15 15:32, Justin Wilson - MTIN wrote: > I was in a discussion the other day and several Tier2 providers were > talking about the idea of adjusting their BGP filters to accept > prefixes smaller than a /24. A few were saying they thought about > going down to as small as a /27. This was mainly due to more > networks coming online and not having even a /24 of IPv4 space. The > first argument is against this is the potential bloat the global > routing table could have. Many folks have worked hard for years to > summarize and such. others were saying they would do a /26 or bigger. > > However, what do we do about the new networks which want to do BGP > but only can get small allocations from someone (either a RIR or one > of their upstreams)?
Any RIR - or LIR - that considers allocating space in sizes smaller than a /24 (for the purpose of announcing to the DFZ) would do well to read this report from RIPE Labs: https://labs.ripe.net/Members/emileaben/has-the-routability-of-longer-than-24-prefixes-changed tl;dr: it's still a bad idea to allocate smaller than a /24. On top of this, I've recently seen some figures that put a 'regular' BGP table mix, at over half of the prefixes received (from numerous upstreams) as being /24s. I really don't want to see everyone already de-aggregating their /18s to /24s, to then go and de-aggregate down to /27s instead. Whilst getting routers with *big RIBS* for little monies, is easy (i.e. Linux box + Quagga). Getting routers that have all the features SPs need, with the throughput requirements too, /and/ have plenty of *FIB* space - that's expensive. Super expensive. -- Tom