Router R1, a branch router, connects to the Internet using DSL. Some traffic flows through a
GRE and IPsec tunnel, over the DSL connection, destined for an Enterprise network. Which
of the following answers best describes the router’s logic that tells the router, for a given
packet, to apply GRE encapsulation to the packet?

A.
When the packet received on the LAN interface is permitted by the ACL listed on the
tunnel gre acl command under the incoming interface

B.
When routing the packet, matching a route whose outgoing interface is the GRE tunnel
interface

C.
When routing the packet, matching a route whose outgoing interface is the IPsec tunnel
interface

D.
When permitted by an ACL that was referenced in the associated crypto map

Explanation:
As for the correct answer, the process of routing a packet out a GRE tunnel interface
triggers the GRE encapsulation action. As for the incorrect answers: There is no
tunnel gre acl command. There is no IPsec tunnel interface. Finally, one answer refers
to logic that would describe a router’s logic when determining whether to encapsulate
a packet into an IPsec tunnel.