nanog mailing list archives
Re: Disaster recovery using as-prepend?
From: Todd Vierling <tv () duh org>
Date: Fri, 17 Feb 2006 16:57:12 -0500 (Eastern Standard Time)
On Fri, 17 Feb 2006, Christopher L. Morrow wrote:
If your primary is connected to ISP_A and the backup is connected to ISP_B, customers connected to ISP_B MAY still flow to your backup DC (ISP_B will probably set local preference on all customer routes - you should be able to override this behavior with communities but not all providers support this (or honor it 100% of the time!))And in addition to that, even multihomed customers of ISP_B may choose the prepended route for a number of different reasons; for instance, ISP_B might be a cheaper pipe for them, or there may be a smart-ish routing device or scheme in play that overrides normal BGP decision making.I might be crazy, but couldn't you just prepend the route enough to effectively poison it at ingress to 'backup-isp' ?
Some route decision override schemes don't care what the path length is at all, or factor it in with such a low weight, such that no reasonable amount of prepending will change the situation. With the development of source traffic engineering schemes, prepending is no longer reliable as a means of affecting routing on the remote side. That perception will have to die with it (hopefully sooner rather than later). -- -- Todd Vierling <tv () duh org> <tv () pobox com> <todd () vierling name>
Current thread:
- Disaster recovery using as-prepend? Christopher J. Pilkington (Feb 16)
- Re: Disaster recovery using as-prepend? Andy Davidson (Feb 16)
- Re: Disaster recovery using as-prepend? Florian Weimer (Feb 16)
- Re: Disaster recovery using as-prepend? Ejay Hire (Feb 16)
- Re: Disaster recovery using as-prepend? Warren Kumari (Feb 16)
- Re: Disaster recovery using as-prepend? Todd Vierling (Feb 17)
- Re: Disaster recovery using as-prepend? Christopher L. Morrow (Feb 17)
- Re: Disaster recovery using as-prepend? Todd Vierling (Feb 17)
- Re: Disaster recovery using as-prepend? Todd Vierling (Feb 17)
- Re: Disaster recovery using as-prepend? Warren Kumari (Feb 17)
- Re: Disaster recovery using as-prepend? Christopher L. Morrow (Feb 17)
- Re: Disaster recovery using as-prepend? Todd Vierling (Feb 17)