I'm in the process of designing some backup routing for a eBGP routing infrastructure. I'm having remote sites connect over a backup link to be used in the event of a carrier failure. This works great, but having both paths up the preferred BGP route is the backup link (even with the local pref and metric forced to high numbers). From what I can tell it's because the AS path over the backup link is shorter than over the carrier backbone. In a Cisco document it says you can have BGP ignore this attribute by using "bgp bestpath as-path ignore," but this isn't supported on IOS 12.4. How can I make the preferred routes the ones that have the longer AS path?