maximum ipv4 bgp prefix length of /24 ?

Sun Oct 1 10:48:33 UTC 2023

On Sat, Sep 30, 2023 at 8:04 PM Owen DeLong via NANOG <nanog at nanog.org> wrote:
> Not sure why you think FIB compression is a risk or will be a mess. It’s a pretty straightforward task.

Hi Owen,

There are multiple levels of FIB compression. The simplest version
merely aggregates adjacent routes with the same next hop.
Straightforward, as you say.

However, there are more advanced versions of FIB compression as well.
Routers have an implicit default route to a drop-and-report target.
Pragmatically, though, the user doesn't really care what happens to
unroutable packets: they can't reach a destination regardless. If you
replace that implicit default route with a "don't care," you can roll
up the entire address space into a set of "send everything to this
next hop with these exceptions." And you can build on that recursively
to get extraordinary FIB compression.

This latter version, however, is not straightforward. Bugs that escape
QC are quite a bit more likely.

Will Juniper stop with the simplest version of FIB compression where
not much can go wrong? Not if it works and customers like it.

Regards,
Bill Herrin

--
William Herrin
bill at herrin.us
https://bill.herrin.us/