nanog mailing list archives
Re: BGP Filtering
From: Deepak Jain <deepak () ai net>
Date: Tue, 15 Jan 2008 17:08:52 -0500
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
Current thread:
- BGP Filtering Ben Butler (Jan 15)
- Re: BGP Filtering Jared Mauch (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- Re: BGP Filtering Joe Abley (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- Re: BGP Filtering Dave Israel (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- Re: BGP Filtering Dave Israel (Jan 15)
- Re: BGP Filtering William Herrin (Jan 15)
- Re: BGP Filtering Dave Israel (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- Re: BGP Filtering Jared Mauch (Jan 15)
- Re: BGP Filtering Deepak Jain (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- RE: BGP Filtering Mike Walter (Jan 15)
- RE: BGP Filtering Ben Butler (Jan 15)
- RE: BGP Filtering Jon Lewis (Jan 15)
- Re: BGP Filtering Christopher Morrow (Jan 15)
- Re: BGP Filtering Jon Lewis (Jan 15)
- Network Operator Groups Outside the US Rod Beck (Jan 16)
- Re: Network Operator Groups Outside the US Suresh Ramasubramanian (Jan 16)
- Re: Network Operator Groups Outside the US Fredy Kuenzler (Jan 16)