nanog mailing list archives
Re: BCP38 For BGP Customers
From: William Herrin <bill () herrin us>
Date: Mon, 7 Nov 2022 13:34:41 -0800
On Mon, Nov 7, 2022 at 12:30 PM Tony Wicks <tony () wicks co nz> wrote:
use prefix lists to prevent your customer networks being received anywhere but directly from your customers to prevent them using your capacity without paying for it however.
Hi Tony, Do not do this either as it will render your entire network unreachable to your customer during an outage of their direct circuit. Multihomed means you may legitimately receive their prefix announcement from both their direct link and from your upstream transit provider. You CAN, tag announcements received directly from your customers with a BGP community and then filter routes without that tag when offering the announcement to your upstream transits. That will have the effect you're looking for - preventing inappropriate free transit. This is rarely necessary - unless your network is unusually complex the additional AS path length of a rebroadcast announcement will generally prevent such transrouting. The problem tends to creep in when you have both reciprocal peers and customers and then a customer's route announcement appears via the peer. You have to make sure the announcement from the peer is neither capable of being rebroadcast upstream nor capable of beating the direct announcement when the direct announcement is present. That takes some subtle work with BGP communities and route filtering. How subtle? The routes from the peer may be more specific than the direct routes. Regards, Bill Herrin -- For hire. https://bill.herrin.us/resume/
Current thread:
- BCP38 For BGP Customers Charles Rumford via NANOG (Nov 07)
- Re: BCP38 For BGP Customers Matt Harris (Nov 07)
- Re: BCP38 For BGP Customers Tom Beecher (Nov 07)
- Re: BCP38 For BGP Customers Jared Mauch (Nov 08)
- Re: BCP38 For BGP Customers Chris Adams (Nov 07)
- Re: BCP38 For BGP Customers William Herrin (Nov 07)
- RE: BCP38 For BGP Customers Tony Wicks (Nov 07)
- Re: BCP38 For BGP Customers William Herrin (Nov 07)
- RE: BCP38 For BGP Customers Tony Wicks (Nov 07)
- Re: BCP38 For BGP Customers Mike Hammett (Nov 07)
- RE: BCP38 For BGP Customers Ryan Hamel (Nov 07)
- RE: BCP38 For BGP Customers Brian Turnbow via NANOG (Nov 08)
- Re: BCP38 For BGP Customers Joel Halpern (Nov 08)
- Re: [EXTERNAL] Re: BCP38 For BGP Customers Compton, Rich A (Nov 08)
- Re: [EXTERNAL] Re: BCP38 For BGP Customers Joel Halpern (Nov 08)
- Re: BCP38 For BGP Customers Jay R. Ashworth (Nov 08)
- Re: BCP38 For BGP Customers Grant Taylor via NANOG (Nov 08)
- Re: BCP38 For BGP Customers William Herrin (Nov 08)