Route table growth and hardware to the filter

Leo Bicknell bicknell at
Sat Sep 8 03:45:18 UTC 2007

In a message written on Fri, Sep 07, 2007 at 07:14:01PM -0400, Jon Lewis wrote:
> For some reason, today I started out with fewer routes (228289...yesterday, 
> I started with 230686) with no filtering.
> RIR filter section	Reduction in routes
> APNIC			16690
> ARIN			41070
> RIPE			16981
> LANIC			 4468
> AFRINIC			 1516
> -----------------------------
> TOTAL			80725
> The end result of applying all the RIR minimum allocation filters was 
> 147564 BGP routes.  I haven't checked to make sure there was no loss in 
> reachability...this is just an idle 7206/NPE225 with nothing but its 
> ethernet uplink.

The CIDR report states that we have 235647 routes that could be
aggregated to 154503 routes.  While not the same metric, I'd be
surprised at 147,564 routes if you did not have reachability issues.

> The prefix-list I'm using for this experiment is:

One idea I've seen tossed around is to allow for a small amount of
deaggregation.  For instance, if in a /8, the RIR allocates down
to a /20, you might allow a /21 (break it into two blocks) or a /22
(break it into four blocks).  Yes, that allows people with bigger
allocations to break into more blocks, but it also allows everyone
to do some TE without letting them do an unlimited amount.

I fear some filtering is in our future.  I'm not really opposed to it,
either.  However I'm afraid your results show the currently available
filters to be too aggressive.

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
Read TMBG List - tmbg-list-request at,
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