Which command adds a rule to drop all input traffic?

Which command adds a rule to drop all input traffic?

• A. /ip firewall filter add chain=input action=drop
• B. /ip firewall filter add chain=input protocol=tcp dst-port=22 action=drop
• C. /ip firewall filter add chain=forward action=drop
• D. /ip firewall filter add chain=output action=drop

Answer: (A)

The main idea is that input traffic is the packets destined for the router itself. To drop everything trying to reach the router, you need a rule in the input chain with an action of drop. The command that adds a firewall filter rule in the input chain and sets the action to drop does exactly that, creating a catch-all that blocks any input to the device. The other options target only specific traffic, such as SSH on port 22, or apply to different contexts (forward traffic, which passes through the router to another destination; or output traffic, which the router itself generates). Those would not drop every bit of input traffic to the router, so they aren’t suitable for a blanket input-drop rule.

The main idea is that input traffic is the packets destined for the router itself. To drop everything trying to reach the router, you need a rule in the input chain with an action of drop. The command that adds a firewall filter rule in the input chain and sets the action to drop does exactly that, creating a catch-all that blocks any input to the device.

The other options target only specific traffic, such as SSH on port 22, or apply to different contexts (forward traffic, which passes through the router to another destination; or output traffic, which the router itself generates). Those would not drop every bit of input traffic to the router, so they aren’t suitable for a blanket input-drop rule.