Final answer:
When a Cisco router encounters a packet with a destination network that's not in its routing table, it will typically discard the packet. Option A (forwarding based on source address), B (sending an ARP request), and C (forwarding via ARP table) are not standard router behaviors in this scenario. The correct behavior is aligned with standard IP network procedures.
Step-by-step explanation:
When the destination network is not listed in the routing table of a Cisco router, the possible action that the router might take is to discard the packet. This occurs because the routing table does not contain a route to the destination network, and without a specific route or a default route (sometimes referred to as the "gateway of last resort"), the router cannot determine where to forward the packet.
Hence, to prevent potential routing loops and to follow standard operating procedures of IP networks, the router will usually drop the packet.
Options A, B, and C are not typical behaviors for a router handling a packet with an unknown destination network:
- Option A is incorrect because routers do not forward packets based on the source address but rather on the destination address.
- Option B is incorrect because ARP (Address Resolution Protocol) is used to map IP addresses to physical MAC addresses within the same network and is not used in routing decisions to external networks.
- Option C is also incorrect because the ARP table or ARP cache is used for local network layer address resolutions and not for routing to external networks.