You have been asked to establish a design that will allow your company to migrate from a WAN service to a Layer 3 VPN service. In your design, you are keeping some WAN links between critical sites as a backup for this service. You plan to use OSPF as your IGP and BGP for the PE-CE protocol. When the Layer 3 VPN service is available, how will you prevent transit traffic over the backup links?
A. Redistribute routes at the CE as external type 1.
B. Redistribute routes at the CE as external type 2.
C. Use conditional advertisement only when the Layer 3 service is down.
D. Manually turn off the backdoor link when the Layer 3 service is up.
