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Thread Index Re: [isp-bgp] filtering pratice
On Tue, May 24, 2005 at 09:49:32PM +0200, Daniel Schild wrote: > Hi, > > I'm just about to peer with another isp, and now i'm wondering what's > the best filtering pratice when it comes to peering. Do i just allow > everything from the other isp, hoping that they don't mess up? the most > important thing is to have some kind of control of what routes they give > us, since we don't want to end up with them giving us a full table or > something like that. > > The first thing i can think of is filtering on as-path, but i know they > have other customers with their own asns. Of course i could always > filter on the as + 1, but i just want to hear about what the most common > pratice in this case is. Also, they have a couple of ip blocks, so we don't > want to filter on their blocks (if we do, we also have to know if > anything changes). Also, i don't know if any of their customers as's have > customers with their own asns, and so on (probably not very likely). > > So, how much do you people filter from your peers? > > > best regards, > daniel > The current best practice is as follows: 1. Strictly filter your BGP customers on both prefix-lists and AS_PATH. 2. Loosely filter your peers -- i.e. place a generic "one-size-fits-all" type of prefix-list, that will block prefixes longer than /24, or any other martian prefixes like RFC1918 as desired. Also place a loose filtering AS_PATH filter, such as one blocking private ASNs but not much of anything else. 3. Place maximum-prefix limit on your peers to a value that is appropriate. Obviously if your peer is a small ISP with only a few prefixes, it may be a good idea to strictly filter them as well. But strict filtering starts getting difficult to manage as number of peers increase and as you peer with larger peers. -J -- James Jun Infrastructure and Technology Services TowardEX Technologies Office +1-617-459-4051 x179 | Mobile +1-978-394-2867 james@... To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. Attn: Discussion List Management 475 Park Avenue South New York, NY 10016 Please include the email address which you have been contacted with. Copyright 2005 Jupitermedia Corporation All Rights Reserved.
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