Maybe I'm oversimplifying. Its Saturday and entirely possible I'm not thinking on all brain cells ($clue--). When it comes to an FIB, there are only say 100-200 destinations on a big router (outbound). Irrespective of the 2M or 20M routes it has. Even though the entire Internet isn't aggregated the way it should be, for FIB purposes, the router knows how it will route out to its 100-200 destinations (ports). Couldn't it just aggregate before it drops routes into its FIB and only import specifics (deagg) if a destination changes for a more specific prefix [like the swamp]? We talk about default-free zones as needing every prefix, and they do (for propagation purposes) but for FIB purposes, they really don't. So they keep a Zebra or OpenBGPd like process (thinking Juniper) that contains *everything* and handles propagation and then each FIB gets an aggregated entry dumped into each FIB on each routing card. This scales very well on the order of a well aggregated internet, and even networks with lots of customer routes (internally or because of lots of customer transit connections) each router only deals with getting the packet to its neighbor. Server CPUs & RAM can handle lots of updates on a 10MM route table all day long. FIBs only need to get involved if the update will change their view of a route -- a central CPU (or cluster of them) can decide that before the FIB sees it. If this isn't clear, I can probably explain it better, but basically what I am saying is that instead of aggregated the FIB based on CIDR rules or expecting total conformity, the router just aggregates from its point-of-view -- if an aggregate to multiple disparate netblocks all goes to the same place, it puts an aggregate in. For example, a router with only 1 connection (no matter how many routes being sent by its upstream), would only have 1 route entered into its FIB -- because no matter where the route goes, it can go upstream. If it feeds a route table to another router, the downstream will see the whole route table irrespective. I know the above degenerate case doesn't address bogons, but really we are only talking about a few dozen extra entries into an FIB for them. Deepak Jain AiNET