On 10/7/23 14:32, Willy Manga wrote:
How about we educate each other to not assume you must deaggregate
your prefix especially with IPv6?
I see 'some' (it's highly relative) networks on IPv4, they 'believe'
they have to advertise every single /24 they have. And when they start
with IPv6, they replicate the same mindset with a tons of /48 . You
can imagine what will happen of course.
A better alternative IMHO is to take advantage to the large prefix
range and advertise a sub-aggregate when necessary. But absolutely not
each end-node or customer prefix.
There are a number of operational reasons folk de-aggregate. I do agree
that there is some behaviour around de-aggregating by default in IPv4
that transferred to IPv6. But the main issue is that most people only
consider the state of their own FIB situation. They hardly consider the
FIB state of other network operators around the world.
As an operator, you have to consciously decide that you will not
de-aggregate any of your allocations. Of course, there is a cost to that
as well, so that cannot be ignored. We, for example, do not de-aggregate
any of our allocations (AS37100), but we can afford to do so because we
always ensure all peering and transit exit/entry points have the same
bandwidth (TE being the main reason networks de-aggregate). Not all
shops can afford that.
Network operations workshops abound where we teach about de-aggregation,
when it can be necessary, and why it should generally be avoided unless
in the most extreme of circumstances. However, in real life, even
engineers that have been through the workshop ringer tend to prefer to
de-aggregate without caution to the FIB state of other autonomous
systems. That said, I do agree that, perhaps, network operations
workshops could emphasize the reluctance to unnecessarily de-aggregate
in light of the increasing cost of having to maintain FIB's.
Mark.
