On Mon, Oct 10, 2022 at 7:58 AM Edvinas Kairys <edvinas.em...@gmail.com> wrote: > We're considering to buy some Cisco boxes - NCS-55A1-24H. That box has > 24x100G, but only 2.2mln route (FIB) memory entries. In a near future it will > be not enough - so we're thinking to deny all /24s to save the memory. What > do you think about that approach - I know it could provide some misbehavior. > But theoretically every filtered /24 could be routed via smaller prefix /23 > /22 /21 or etc. But of course it could be a situation when denied /24 will > not be covered by any smaller prefix. > > What do you think about this approach ?
If you have a default route that works and you don't have any downstream customers which expect a full routing table, this is fine. You just won't get as good results with the /24s. Beware that MOST Internet /24 routes are NOT covered by a shorter prefix so unless you specifically cover them they will be lost. This will severely impact your Internet connectivity. The Internet FIB is around 900k IPv4 routes. You have years before exhausting a 2.2M table. Regards, Bill Herrin -- For hire. https://bill.herrin.us/resume/
