Hi A conditional route in BGP is basically a route that will be advertised based on the conditions that another route is already there and valid , mostly used when you have dual ISPs or more in mutli homed designs , the doc below shows a working example, you can also use NULL0 with static routes and advertise conditional routes that way too
The Border Gateway Protocol (BGP) conditional advertisement feature provides greater control over route advertisements by permitting certain routes to be advertised based on the existence of other routes in the BGP table. This is a useful feature for multi-homed networks when it is desirable to advertise certain networks to one of the Internet Service Providers (ISPs), but only if the connectivity to another ISP fails
https://routingnull0.com/2014/05/27/hour-440-bgp-conditional-route-injection/
http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/16137-cond-adv.html
