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

[Mike Hammett <nanog () ics-il net>]

My assumption is that it's not a one-and-done scenario - that the middleware continually adjusts. 




----- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 

Midwest-IX 
http://www.midwest-ix.com 

----- Original Message -----

From: "Elmar K. Bins" <elmi () 4ever de> 
To: "NANOG Operators' Group" <nanog () nanog org> 
Sent: Monday, October 10, 2022 10:48:56 AM 
Subject: Re: any dangers of filtering every /24 on full internet table to preserve FIB space ? 

nanog () ics-il net (Mike Hammett) wrote: 

> Feasibility of adding some middleware that culls unneeded routes (existing more specific and aggregate routes 
> pointing to the same next hop), when that table starts to fill? 

Well... if that covering prefix goes away, let's hope you still have a default. 

I've (been forced to) cull long prefixes on some memory-starved routers, and 
given that all of them have defaults, For our (former employers and certainly 
the current one) I've seen moderate to no traffic shifting, and this approach 
gave the museum gear another lease on life - they were fine with bandwidth. 
I've even gone down to strip anything longer than a /20 in v4, and a /40 in v6. 

If you run a backbone that needs to know the best exit for a prefix in order to 
throw traffic out locally and not pay good money for sightseeing capacity, you 
might fare better with beefier routing engines. 

El Mare.