nanog mailing list archives
Re: AS Path Loops in practice ?
From: Jeff Aitken <jaitken () aitken com>
Date: Thu, 11 Dec 2003 22:41:19 -0500
On Thu, Dec 11, 2003 at 11:07:03PM +0000, Stephen J. Wilcox wrote:
Perhaps I'm missing something having not done this myself but why arent the customers just using private ASNs? That would also remove the 'must default' clause.
What if you have more customers than there are private ASNs? Think about things like 2547-style VPNs, etc. What if you want to propogate those customers' BGP announcements to the world? Which hardware vendors support a "strip-private-ASN" feature? Did they always do so? If every such customer uses a private ASN, every other default-free customer must accept routes from the ISP that contain private ASNs in the as-path. Which of your default-free customers might be filtering those prefixes? It makes it a little more difficult for the ISP to filter prefixes with private ASNs in the path; those from some customers must be honored; those from other customers and from peers should be dropped. The ones that were supposed to be honored should be passed along to other BGP-speaking customers but not to peers. This is obviously not an insurmountable problem, but it does add a lot of config complexity. Private-ASN collisions (i.e., when one customer uses one ASN to talk to the ISP and another ASN internally which the provider assigns to a different customer) will cause problems. You WILL hear this from a customer: "I want to use ASN X for this purpose because that's what my consultant said." Repeat, but s/a customer/another customer/. Etc. --Jeff
Current thread:
- AS Path Loops in practice ? Jaideep Chandrashekar (Dec 08)
- Re: AS Path Loops in practice ? Robert E. Seastrom (Dec 08)
- Re: AS Path Loops in practice ? Joe Provo (Dec 08)
- Re: AS Path Loops in practice ? Robert E. Seastrom (Dec 08)
- Re: AS Path Loops in practice ? Joe Provo (Dec 08)
- Re: AS Path Loops in practice ? Ben Crocker (Dec 09)
- Re: AS Path Loops in practice ? Niels Bakker (Dec 09)
- Re: AS Path Loops in practice ? Leo Bicknell (Dec 09)
- Re: AS Path Loops in practice ? Niels Bakker (Dec 09)
- Re: AS Path Loops in practice ? Stephen J. Wilcox (Dec 11)
- Re: AS Path Loops in practice ? Leo Bicknell (Dec 11)
- Re: AS Path Loops in practice ? Jeff Aitken (Dec 11)
- Re: AS Path Loops in practice ? David Barak (Dec 11)
- Re: AS Path Loops in practice ? Stephen J. Wilcox (Dec 12)
- Re: AS Path Loops in practice ? David Barak (Dec 12)
- Re: AS Path Loops in practice ? Niels Bakker (Dec 09)
- Re: AS Path Loops in practice ? Robert E. Seastrom (Dec 08)