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

Nick Suan nsuan at
Mon Oct 10 15:25:59 UTC 2022

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
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