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

[Nick Suan via NANOG <nanog () nanog org>]

There's 69,055 pure /24's allocated or assigned directly from an RIRs. At least c,d,e, and g root servers only have 
/24s allocated to them. Major services like Cloudflare only advertise the /24 without advertising an aggregate. 

Unless you're also getting a default from upstream, it sounds like you're going to end up wasting the money you saved 
on chasing down subtle brokenness. 

On Mon, Oct 10, 2022, at 9:58 AM, Edvinas Kairys 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