Which of these accurately describes dial backup routing?
it always uses distance vector routing protocols
once the backup link is activated it will remain active even after the primary link is restored
it always uses permanent static routes
it is supplied by the service provider as a secondary PVC at no additional charge
the router intiates the dial backup link when a failure is detected on the primary link
WAN Backup Design
Redundancy is critical in WAN design for the remote site because of the unreliable nature of WAN links, when compared to LANs that they connect. Most enterprise edge solutions require high availability between the primary and remote site. Because WAN links have lower reliability and
lack bandwidth, they are good candidates for most WAN backup designs.
Branch offices should have some type of backup strategy in the event of a primary link failure. Backup links can be either dialup, permanent WAN, or Internet-based connections.
WAN backup options are as follows:
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 7