SRX devices operate on adefault deny-all policyif no explicit match is found:

If a packet does not match any configuredzone-basedorglobalpolicy, it is implicitly denied.

The traffic is discarded silently by the default security policy (Option A).

Option B:No predefined “safe zone” exists.

Option C:Logging occurs only if explicitly configured; default deny does not automatically log traffic.

Option D:Incorrect, since the firewall defaults to deny, not permit.

Correct Behavior:Traffic is discarded by the default security policy.

NAT processing in Junos OS follows a strict sequence to ensure correct packet handling:

Static NAT– applied first because it provides a permanent one-to-one bidirectional mapping.

Destination NAT– applied second to translate inbound destination addresses, often used for servers in private networks.

Source NAT– applied last to translate outbound private source addresses to public ones.

This ensures deterministic behavior and avoids conflicts between translation types.

Options B, C, and D list incorrect sequences.

Correct Order:static NAT → destination NAT → source NAT

Routing instances:Security zones are local to their routing instance. Theycannot be shared between routing instances(Option B is correct). Each routing instance must define its own zones.

Intrazone and interzone traffic:Both types of traffic require policies in Junos OS. Intrazone traffic must have an explicit intra-zone policy to be controlled (Option C is correct).

Sharing zones:Option A is incorrect, as zones cannot span routing instances.

Multiple zones:SRX devices fully support multiple security zones (trust, untrust, DMZ, etc.). Option D is incorrect.

Correct Statements:B and C

From the exhibit:

The internal host (172.25.11.101) is located in theTrust zone.

The external address (203.0.113.199/30) is used for communication with the ISP.

The requirement is thatsessions can only be initiated from the external device(the ISP or untrust side) toward the internal host.

This requirement matches the behavior ofDestination NAT:

Destination NAT only (Option A):Maps the external/public IP (203.0.113.199) to the internal/private IP (172.25.11.101). This allows inbound connections to be translated and sent to the internal host. The internal host cannot initiate outbound sessions, since the translation only applies to inbound traffic.

Source NAT only (Option B):Used for outbound sessions from internal private IPs to the Internet. This does not meet the requirement.

Static PAT (Option C):Maps a single port of a public IP to a private IP/port. The exhibit does not indicate a port-based translation.

Static NAT and source NAT (Option D):Would provide bidirectional communication, allowing sessions to be initiated in both directions. This contradicts the requirement.

Correct NAT Type:Destination NAT only

In Junos OS, NAT rules are evaluated intop-down order. When a new rule is added, it is placed at thebottomof the rule set by default.

To move a rule to the top of the rule set, the command is:

set security nat source rule-set rule top

Option A (top):Correct. Moves the specified rule to the top of the list.

Option B (run):Used to execute operational commands, not rule reordering.

Option C (up):Not valid for reordering NAT rules.

Option D (insert):Not a supported NAT reordering command in Junos.

Correct Command:top

When two networks use the same private IP address ranges, conflicts occur. The solution is to use address translation techniques on the SRX:

NAT (Network Address Translation):Translates private IP addresses to another IP range, enabling connectivity between overlapping private networks.

PAT (Port Address Translation):Extends NAT by allowing multiple private IPs to share one or a few public IPs using different port numbers. This is especially useful when there is a limited pool of public IP addresses.

Other options:

IDP (Option A):Intrusion Detection and Prevention, unrelated to address overlap.

BGP (Option C):A routing protocol, but it does not solve overlapping IP addressing problems.

Correct Features:NAT and PAT

NextGen Web Filtering (NGWF) requires SSL proxy functionality to inspect HTTPS traffic. To enable NGWF:

Option B:You can generate aself-signed certificatefor SSL proxy functionality (or import a CA-signed certificate, but the course emphasizes self-signed for lab/demo purposes).

Option D:You must configure anSSL proxy profileso that HTTPS traffic can be decrypted and inspected.

Option A:A CA-signed certificate may be used in production but is not strictly required to enable NGWF.

Option C:SSL initiation profiles are used for outbound SSL inspection initiated by the SRX, not for NGWF traffic interception.

Correct Actions:Generate a self-signed certificate, Configure an SSL proxy profile