Cisco 200-125 Exam: How Routers Handle Incoming Packets with Missing Destination Networks

How Routers Handle Incoming Packets with Missing Destination Networks

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Question

How does a router handle an incoming packet whose destination network is missing from the routing table?

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Explanations

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A. B. C. D.

Explanation

When a router receives an incoming packet, it looks up the destination network in its routing table to determine the appropriate interface to forward the packet. If the destination network is not found in the routing table, the router will handle the packet in one of the following ways:

C. It routes the packet to the default route: The default route is a special entry in the routing table that specifies the next hop for any packet whose destination network is not explicitly listed in the routing table. If the router has a default route configured, it will forward the packet to the next hop specified in the default route entry. This next hop is typically the IP address of another router that has more information about the destination network.

A. It broadcasts the packet to each interface on the router: In some cases, the router may be configured to forward packets to all interfaces on the router if the destination network is not found in the routing table. This is known as a broadcast storm and can cause excessive network traffic and slow down the network.

D. It discards the packet: If the router is not configured to forward packets to all interfaces or does not have a default route configured, it may simply discard the packet and send an ICMP (Internet Control Message Protocol) message back to the source indicating that the destination network is unreachable.

B. It broadcasts the packet to each network on the router: This is not a valid option for how a router handles a packet with a missing destination network. A router will not broadcast a packet to each network on the router, as this would also cause a broadcast storm and could bring down the network.