JN0-232: Security, Associate (JNCIA-SEC)

Junos OS applies static NAT before destination NAT, and it applies source NAT later in packet processing, after route and security-policy lookup. Static NAT therefore takes precedence over destination NAT, which takes precedence over source NAT.

Junos OS is Juniper’s network operating system and powers Juniper physical and virtual networking and security products. It is distinct from a network management system and is not an IoT-specific operating system.

SRX Series Firewalls support flow mode, which processes traffic according to flow or session state, and packet mode, which processes traffic on a per-packet, stateless basis.

Junos OS uses the insert configuration command to reposition a NAT rule before or after another rule in its rule set. This allows a newly added rule at the bottom of the list to be placed in the required evaluation order.

SRX security policies are selected using the packet’s incoming security zone, determined by its ingress interface, and outgoing security zone, determined by the forwarding lookup. Confirming that those interfaces are assigned to the intended zones is therefore the next step before evaluating the applicable security policy or later processing such as NAT and ALGs.