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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: BGP Filtering
But if I can see the /19 in the table, do I care about a load of /24s because the whole of the /19 should be reachable as the origin AS is announcing it somewhere in their network and it is being received my a transit so should be reachable. The "presumption" in cases like this is that the /24 may take a different path than the /19 in some or all cases. If you have only a single provider you can safely dump more specifics -- but then, you could just point default. If you *are* multihomed and the /19 and /24 both have the same primacy (first choice in a routing decision and same path) you can safely drop the more specific. The "presumption" is that in some cases the /24 would take a different path than the /19 in a routing fight. How much cost you want to incur for these is your choice. If enough people drop the more specifics, they will go away as well -- if they provided no benefit, fewer would exist. Some of this originates from the peering-contests where folks have "x number of prefixes" which makes them bigger than "y number of prefixes". I'd be interested to see any metrics on rate of growth of allocations longer than RIR limits since Verio instituted then dropped mandatory prefix filters. (vs the rate of growth of prefixes overall). I would guess that they accelerated. Deepak
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