I suppose that would depend on what ISPs you're buying transit through. Technically, the smallest block you can announce that won't be filtered is still /24, a

I suppose that would depend on what ISPs you're buying transit through. Technically, the smallest block you can announce that won't be filtered is still /24, and many do, including networks that punch holes in their own aggregates, or their upstream ISPs' aggregates for redundancy, etc. However, with the global BGP table coming in at just shy of 300,000 routes now, there's pressure to filter small prefixes more and more. There's kind of a de facto gentleman's agreement among the sorts of folks that are in NANOG that /22 should be the new de facto "smallest prefix" wherever possible. I really think getting your /24 announced and propagated (if it's truly a provider-independent block from a RIR, e.g. ARIN, and not just a Class C subnet from an ISP network) might be encumbered by hemming and hawing from routing administrators that are constantly keeping the dwindling capacity of existing routers to hold full BGP views - especially multiple full views from multiple peers - in mind. You can definitely do it, but the appeal of a /24 is slightly diminished in light of that.