You can also do this (Equal Cost MultiPath to servers) without a dynamic routing protocol but you are at the mercy of whatever health checks your top of rack switch supports.
On Cisco switches you can use a IP SLA check to monitor for DNS replies from a DNS server and then have a static route that tracks the SLA check. If your DNS server stops responding the route would be withdrawn and traffic routed away. This can happen within a few seconds.
Slides from a NANOG talk about this (PDF): http://www.nanog.org/meetings/nanog41/presentations/Kapela-l...
On Cisco switches you can use a IP SLA check to monitor for DNS replies from a DNS server and then have a static route that tracks the SLA check. If your DNS server stops responding the route would be withdrawn and traffic routed away. This can happen within a few seconds. Slides from a NANOG talk about this (PDF): http://www.nanog.org/meetings/nanog41/presentations/Kapela-l...