What is an appropriate use of a default route?（）

A.to verify the type of cable interconnecting two devices
B.to determine the status of network services on a remote device
C.to obtain VLAN information from directly connected switches
D.to verify Layer 2 connectivity between two devices when Layer 3 fails
E.to obtain the IP address of a connected device in order to telnet to the device
F.to determine the status of the routing protocols between directly connected routers

A.Passive routes are in the process of being calculated by DUAL.
B.EIGRP supports VLSM, route summarization, and routing update authentication.
C.EIGRP exchanges full routing table information with neighboring routers with every update.
D.If the feasible successor has a higher advertised distance than the successor route, it becomes the primary route.
E.A query process is used to discover a replacement for a failed route if a feasible successor is not identified from the current routing information.

A.Broadcasts only use network layer addressing.
B.A broadcast frame is never forwarded by a switch.
C.A broadcast address will never be the source address of a frame.
D.Broadcast addresses use an incorrect format for the switching table.
E.Broadcast frames are never sent to switches.