JN0-232 Exam Dumps - Security, Associate (JNCIA-SEC)

In Junos OS, NAT rules are evaluated in top-down order . When a new rule is added, it is placed at the bottom of 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 < name > rule < rule-name > 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

Security policies in Junos OS match traffic based on specific criteria:

Source and destination addresses (Option B).

Application (Option D), which may be defined as services (e.g., tcp/80) or recognized through AppID.

Other options:

MAC addresses (Option A) are not used in policy matching; policies operate at Layer 3/4.

Interface name (Option C) is used in firewall filters, not in security policy definitions.

Correct Criteria: Source address and Applications

The trace output shows that the SRX receives the ICMP packet, does not find an existing session, starts first path processing, and then drops the packet with a firewall check failure before a session is successfully created. In SRX troubleshooting, first path processing includes route lookup, policy evaluation, and session creation. If the device cannot determine a valid forwarding path for the destination, the session cannot be established and the packet is dropped. The exhibit does not show evidence of a web filtering decision, ALG processing, or a screen counter match. Therefore, the best answer is that there is no known route to the destination 192.0.2.128. The appropriate operational verification would be to check the routing table using a command such as show route 192.0.2.128.

When both source NAT and destination NAT are involved, the security policy must match addresses according to Junos NAT processing order. Juniper documents that static NAT and destination NAT are processed before route lookup and security policy lookup, while source NAT is processed after route and security policy lookup. This means that by the time policy evaluation occurs, the destination address has already been translated by destination NAT. However, the source address has not yet been translated by source NAT. Therefore, the correct policy match conditions are the post-NAT destination address and the pre-NAT source address. Matching on the pre-NAT destination or post-NAT source would not align with Junos SRX processing order.

By default, SRX 300 Series Firewalls come with predefined security policies:

Trust-to-Untrust (Option B): A default policy exists to permit all traffic from the trust zone to the untrust zone .

Trust-to-Trust (Option D): Intra-zone traffic is permitted by default; hence, a trust-to-trust policy is installed automatically.

Untrust-to-Trust (Option A): Not allowed by default, since external traffic must be explicitly permitted by an administrator.

Management-to-Trust (Option C): No such default policy exists.

Correct Policies: Trust-to-Untrust and Trust-to-Trust

Destination NAT is the correct answer because it allows an external host to initiate traffic toward an internal resource by translating the destination address of inbound packets. In the exhibit, the requirement is that sessions can only be established from the external side. Static NAT is not the best choice because static NAT is bidirectional; it allows sessions to be originated from either side of the network. Source NAT is normally used for internal hosts initiating outbound access by translating their source address, which does not satisfy the requirement for external-only session establishment. Destination NAT changes the packet’s destination address before security policy evaluation, allowing the SRX to forward external requests to the internal host according to policy.

Global security policies extend the flexibility of policy enforcement across the SRX. They are not tied to specific source and destination zones:

From-zone and to-zone contexts are not required (Option A). Global policies apply across all zones unless restricted by match conditions.

Global security policies do not require specific zone contexts (Option B is incorrect).

Global policies are processed after zone-based policies , not before. This means that zone-based security policies take precedence (Option C is incorrect).

Administrators can configure both zone-based security policies and global security policies at the same time on the same device (Option D is correct).

This allows flexible designs where specific policies can be enforced by zone, while general policies can be applied globally without duplicating rules across multiple zones.

Destination NAT purpose (Option C): Used to allow external hosts on the Internet to access internal/private resources (such as a web server in the DMZ). Destination NAT changes the destination IP of incoming traffic to match the internal server.

Pool-based NAT (Option D): SRX supports destination NAT pools, allowing multiple public IP addresses or ranges to be translated to internal servers.

Incorrect options:

Option A describes source NAT , not destination NAT.

Option B is incorrect because SRX does not support “interface-based” destination NAT.

Correct Statements: C and D