Will a single /27 get fully routed these days?

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Mon Jan 27 05:14:59 UTC 2014

Sander Steffann wrote:

>> i suspect that, as multi-homing continues to grow and ipv4 space
>> fragments to be used in core-facing nat[64]-like things, a decade
>> from now we'll see the boundary move to the right.
> Maybe, if the equipment can handle the number of routes. I actually
> see two opposing things: the scarcity will require more fragmentation
> with smaller fragments, which requires less strict filtering.

The problem is not prefix length (it is a problem if >32, which is
the case with IPv6) but the number of routes, which grows because
of not fragmentation but poor way of multihoming through routing.

Note that if IPv6 will be as popular as IPv4, it has almost equal
number of routes for multihoming.

> On the
> other hand the fragmentation will already start with e.g. /20s being
> fragmented into /24s. That might already cause problems for current
> hardware, which might cause people to filter more strictly.
> Unfortunately my crystal ball is broken at the moment.

Considering that a fast cheap 18bit 16M entry 1 chip SRAM has been
available for many years, route vendors do not have to deploy
slow and complicated logic for route look up, unless they want
to make IPv4 route look up as slow as that of IPv6.

Even 4G entry will not be a problem, except that it may cause BGP
update computation slower.

						Masataka Ohta

More information about the NANOG mailing list