Except we might very well reach 1+ million routes soon without accepting longer prefixes than /24. Also route updates is a concern - do I really need to be informed every time someone on the other end of the world resets a link? On 3 October 2015 at 12:57, William Waites <wwaites@tardis.ed.ac.uk> wrote:
On Sat, 3 Oct 2015 12:42:01 +0200, Baldur Norddahl < baldur.norddahl@gmail.com> said:
> 2 million routes will not be enough if we go full /27. This is > not a scalable solution. Something else is needed to provide > multihoming for small networks (LISP?).
It's not too far off though. One way of looking at it is, for each extra bit we allow, we potentially double the table size. So with 500k routes and a /24 limit now, we might expect 4 million with /27. Not exactly because it depends strongly on the distribution of prefix lengths, but probably not a bad guess.
Also there are optimisations that I wonder if the vendors are doing to preserve TCAM such as aggregating adjacent networks with the same next hop into the supernet. That would mitigate the impact of wanton deaggregation at least and the algorithm doesn't look too hard. Do the big iron vendors do this?
-w
-- William Waites <wwaites@tardis.ed.ac.uk> | School of Informatics http://tardis.ed.ac.uk/~wwaites/ | University of Edinburgh https://hubs.net.uk/ | HUBS AS60241
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