What is the purpose of maintaining an ARP cache in the firewall?

Maintaining an ARP (Address Resolution Protocol) cache in a firewall primarily serves the purpose of minimizing broadcast traffic on the network. When a device wants to communicate with another device on the same local network and only knows its IP address, it needs to resolve that IP address to a MAC address. This is typically done using ARP by broadcasting a request to all devices on the network.

If the firewall has an ARP cache, it can store these resolved IP-to-MAC address mappings, which means that subsequent communications to the same IP address can occur without needing to send out a broadcast request each time. This significantly reduces unnecessary traffic on the local network, which can help optimize performance and efficiency. By minimizing these broadcasts, the firewall can also contribute to a more stable network environment, as excessive broadcast traffic could lead to network congestion.

The other options mention aspects like security enhancements and speed improvements, but the primary and most direct function of the ARP cache is related to traffic management, specifically by reducing the number of broadcast messages required for device communication.