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