Which of the following is most likely to be useful on the branch router?

Router R1 sits at an Enterprise branch office, using both the Internet and a leased line to
another Enterprise router for its two connectivity options back into the rest of the Enterprise
network. The engineer planning for this branch decided to use the leased line for all
Enterprise traffic, unless it fails, in which case the Internet connection should be used to
pass traffic to the Enterprise. Which of the following is most likely to be useful on the branch
router? (Choose two.)

A.
IPsec tunnel

B.
GRE tunnel

C.
Floating static route

D.
An IGP

Explanation:
An IPsec tunnel would be useful to allow the packet to pass over the Internet
and into the EnterprisE. The GRE tunnel would only be needed if an IGP is also
needed, and for this design, an IGP is not requireD. Instead, a floating static default
route would work fine, with the static route sending traffic over the IPsec tunnel but
only when the private leased line fails.