any dangers of filtering every /24 on full internet table to preserve FIB space ?

Mon Oct 10 15:08:38 UTC 2022

On Mon, Oct 10, 2022 at 7:59 AM Edvinas Kairys <edvinas.email at gmail.com>
wrote:

> Hello,
>
> 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 ?
>
> Also maybe you know - some advices for edge routers that have at least
> 8x100G interfaces and "good" memory for prefix count ? Thanks
>
Sounds good to me. Especially , if you are prioritizing ipv6 routes in your
fib

What is your use case ? Selling transit bgp might be tricky since you will
be not sending specifics to your downstreams.

If you are edge network like me, taking a default from your upstream solves
all problems and you can filter and TE as you wish.
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