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

Owen DeLong owen at
Mon Oct 10 16:00:21 UTC 2022

There are most definitely a number of organizations that have /24s that are not part of a larger aggregate.

If you don’t have a default route to some router that takes the full table on your behalf, then you will loose connectivity to/from those entities.


> On Oct 10, 2022, at 07:58 , Edvinas Kairys < at> 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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