In Junos OS, particularly on SRX Series devices, host inbound traffic (traffic destined for the device's Routing Engine) is controlled at the zone and logical interface level. A security zone is a collection of one or more logical interfaces. To permit or deny services like SSH, ping, or SNMP to the device itself, you configure host-inbound-traffic options within a specific security zone. This configuration specifies which system services and protocols are allowed on the logical interfaces assigned to that zone. Therefore, both the zone and the logical interface are fundamental components in this configuration.

C. physical interface: Configuration elements like IP addresses, zone membership, and firewall filters are applied to logical interfaces (e.g., ge-0/0/0.0), not directly to the parent physical interface (e.g., ge-0/0/0).

D. routing instance: A routing instance provides routing and forwarding table separation. While host traffic can exist within an instance, the instance itself is not the component where traffic permissions are directly configured; that is still done on zones/interfaces within it.

1. Juniper Networks Documentation - Understanding Host Inbound Traffic: "You configure host-inbound traffic on a per-zone basis. In the host-inbound-traffic statement

you specify the services and protocols that are allowed for host-inbound traffic on the interfaces in a zone." This directly connects zones and interfaces to the configuration.

URL: https://www.juniper.net/documentation/us/en/software/junos/security-policies/topics/concept/security-host-inbound-traffic-understanding.html

2. Juniper Networks Documentation - [Example] Configuring Zones: "This example shows how to configure security zones and assign interfaces to them... set security zones security-zone trust interfaces ge-0/0/1.0". This shows the assignment of a logical interface (ge-0/0/1.0) to a zone.

URL: https://www.juniper.net/documentation/us/en/software/junos/security-policies/topics/example/security-zone-configuring-cli.html

3. Juniper Networks Documentation - Interfaces Fundamentals: "Junos OS distinguishes between physical and logical interfaces. A physical interface is a physical port on the device... A logical interface is a configurable sub-unit of a physical interface." This clarifies the distinction between physical and logical interfaces.

URL: https://www.juniper.net/documentation/us/en/software/junos/interfaces-fundamentals/topics/concept/interfaces-fundamentals-logical-and-physical-interfaces-overview.html