What is the default behavior of Junos when a packet doesn't match any terms in a firewall filter?

In Junos, the default behavior when a packet does not match any terms in a firewall filter is to silently drop the packet. This is a security feature that ensures any traffic not explicitly allowed by the firewall filter rules is not permitted to pass through the firewall. By dropping unmatched packets, the system maintains a strong security posture by preventing unwanted or potentially harmful traffic from being processed or forwarded.

This behavior is important for network administrators to understand, as it helps in designing firewall filters that carefully specify which traffic should be allowed based on organizational needs. The practice of silently dropping packets avoids unnecessary responses that could potentially reveal network topology or expose the system to additional risks.