JN0-232 Security, Associate (JNCIA-SEC) Questions and Answers

NAT rule processing on SRX devices follows a deterministic order:

Top-to-bottom order (Option C):NAT rules are always evaluated in the order they appear in the configuration, starting at the top.

First-match wins (Option B):Once a packet matches a NAT rule, processing stops.

Option A:Incorrect. Not all rules are processed; evaluation stops at the first match.

Option D:Incorrect. NAT rules are never processed bottom-to-top.

Correct Statements:NAT rule processing stops at the first match, and NAT rules are processed top-to-bottom.

For an SRX firewall interface to respond to management traffic such as ICMP pings:

Theinterface must be assigned to a security zone(Option A). If an interface is not part of any zone, it is placed into the null zone, which drops all traffic.

Additionally, the zone must be configured to allow management traffic types ashost-inbound-traffic(Option D). For ICMP, the protocol must be explicitly allowed under host-inbound-traffic for that zone.

Other options:

Security policies (Option B) control traffic traversing the firewall, not traffic destined to the SRX device itself.

Assigning the interface to the null zone (Option C) prevents any communication, including management.

Correct Actions:Assign the interface to a zone and configure ICMP under host-inbound-traffic.

Source NAT (Network Address Translation) is used on SRX devices to allow hosts with private IP addresses to access external networks, such as the Internet. The SRX translates theprivate IP address of the source host into a public IP addressbefore forwarding traffic toward the destination.

It does not translate MAC addresses (Option A).

NAT is unidirectional in this case: it specifically translates private-to-public in the outbound direction, while the reverse (return traffic) is handled automatically through the session table. It is not a bidirectional translation (Option C).

NAT processing occurs as part of the flow module, not limited only to ingress traffic (Option D).

Therefore, the correct statement is that source NAT translatesprivate IP addresses to public IP addresses.

The SRX Series devices support third-party antivirus scanning engines such asAvira. To use the Avira antivirus engine, administrators must explicitly enable the engine and ensure that the required components are properly loaded.

Enable in configuration mode:

The Avira antivirus engine must be enabled under UTM configuration mode. This step ensures the SRX device uses the Avira scanning engine for antivirus inspection.

Example:

set security utm feature-profile anti-virus avira-engine enable

Reboot the SRX device:

A system reboot is required after enabling the Avira engine to load the Avira antivirus components into memory.

Without a reboot, the Avira engine will not become active.

Why not the others?

Restarting themgdprocess (Option A) only reloads the management daemon and does not load antivirus engines.

Enabling inoperational mode(Option B) is not supported; the configuration must be applied in configuration mode.

Therefore, the correct actions to use Avira Antivirus are:Enable the Avira engine in configuration mode (Option D) and reboot the SRX device (Option C).

When a packet enters an SRX interface, aroute lookupis performed:

It determines theegress interface(Option B) by checking the destination IP against the routing table.

Once the egress interface is known, its associatedegress security zone(Option D) is also determined.

Theingress interface (Option A)is already known when the packet arrives, so the route lookup does not determine it.

DNS name (Option C):DNS is unrelated to routing lookups.

Correct Results:egress interface, egress security zone

Content filtering on SRX devices inspects and controls specific file types transferred across certain application protocols:

SMTP (Option A):Supported. Content filtering can block specific file attachments in emails.

HTTP (Option D):Supported. Content filtering can block downloads of specific file types over web traffic.

SNMP (Option B):Not supported; SNMP is a management protocol, not a content delivery protocol.

TFTP (Option C):Not supported by content filtering.

Correct Protocols:SMTP and HTTP

From the exhibit, the content filter configuration is as follows:

Match Conditions:

Application:HTTP

Direction:download

File-types:exe

Action:

block

notification log

Analysis of Options:

Option A: Incorrect. The configuration specifies thedownload direction, not upload. Uploads of .exe files are unaffected.

Option B: Correct. Because the rule applies todownloads, .exe files will be blocked when users attempt to download them over HTTP.

Option C: Correct. The notification { log; } statement ensures that an entry will be added to the SRX device’s log when the action is triggered.

Option D: Incorrect. No configuration for sending e-mail notifications is shown in the rule. Only logging is specified.

Correct Statements:B and C

In Junos OS, traffic is classified into three main categories:

Transit traffic:

Defined as traffic thatenters one interface and exits another interface.

It is handledentirely in the forwarding plane (Packet Forwarding Engine).

Example: User data packets moving between trust and untrust zones.

Correct →Option A.

Exception traffic:

Traffic requiring processing by theRouting Engine (control plane), such as routing updates or management traffic.

MatchesOption C/D, but that is not transit traffic.

Control traffic:

Management or routing-related, handled by the control plane.

Rate-limiting (Option B):

This applies specifically toexception trafficto protect the Routing Engine, not to transit traffic.

Correct Statement:Transit traffic is traffic that is processed solely through the forwarding plane.

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

To enforce acatch-all blocking policyafter other specific policies, the correct solution is aglobal security policy (Option A).

Global policiescan apply universally across zones, and an administrator can configure a final “deny all” rule to block any unmatched traffic.

ATP policy (Option B):Protects against advanced threats, not used for catch-all rule enforcement.

IDP policy (Option C):Focuses on intrusion detection and prevention signatures, not general traffic blocking.

Integrated user firewall policy (Option D):Applies policies based on user identity, but it does not provide a universal block across all services.

Correct Solution:Global security policy

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 source NAT uses a pool of addresses from thesame subnet as the egress interface, the firewall must respond to ARP requests for those NAT pool IPs. Without this, upstream devices would not know how to forward traffic destined for those IPs.

Proxy ARPis required (Option D). It enables the SRX to answer ARP requests on behalf of the NAT pool addresses.

Static NAT (Option A)is unrelated and maps one-to-one, not required here.

Dynamic DNS (Option B)has no relation to NAT pools.

Destination NAT (Option C)applies to inbound translations, not outbound source NAT pools.

Correct Feature:Proxy ARP

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

When a new packet arrives that does not match an existing session, the SRX performs full flow-based processing. After ingress zone determination, the firewall must know the destination zone to evaluate security policies.

The SRX determines theegress zone by performing a route lookupon the packet’s destination IP address.

The routing decision identifies the outgoing interface, and the zone associated with that interface becomes theegress zone.

Session lookup (Option A) happens first but is only useful for existing sessions.

Destination port (Option B) is used for application identification, not zone determination.

Ingress zone properties (Option D) cannot determine the egress zone.

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

Global policies (Option D):Evaluated before zone-based policies. They allow centralized control and can apply across all zones. Perfect for Internet-to-private traffic that must be enforced before other rules.

Routing policy (Option A):Controls routing decisions, not traffic forwarding/security.

Default policy (Option B):Denies all traffic by default, but cannot be customized for early evaluation.

Zone policy (Option C):Zone-based policies apply after global policies and are limited to specific zone pairs.

Correct Policy Type:Global policy