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

SRX Series devices providecontent securityfeatures that rely on advanced identification mechanisms. File identification is not based merely on file extensions (which can be easily spoofed), but instead ondeep inspection techniques:

AppID (Application Identification):AppID is part of the AppSecure suite, allowing the device to classify applications and content regardless of port or protocol. This enables the SRX to detect applications and their related content for enforcement.

Protocol-based file type identification:The SRX can recognize and identify file types embedded withinHTTP, FTP, and e-mail (SMTP, IMAP, POP3) protocols. This providesaccurate content inspection and filtering, independent of file naming conventions.

Why not the others?

File extensions (Option A) are not reliable for content security, so SRX does not use them.

ALGs (Option D) are used for protocol handling, such as SIP or FTP control channels, not for content identification.

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

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

Juniper SRX evaluatessecurity policies in order, top to bottom. The first matching policy determines the action, and no further policies are evaluated. This behavior can lead toshadowed policiesif later policies match the same conditions as earlier ones.

From the exhibit:

Policy1:Matches application junos-http and permits traffic.

Policy2:Matches application junos-https and permits traffic.

Policy3:Matches application junos-http again, but denies traffic.

Sincepolicy1already matches all HTTP traffic and permits it, traffic never reachespolicy3. This makespolicy3 shadowedbecause it has the same match condition as policy1 but is evaluated later in the list.

Other options:

Policy1 is not shadowed because it is evaluated first.

Policy2 is independent (application = HTTPS) and therefore unaffected.

Only policy3 is shadowed by policy1.

Correct Statement:Policy3 will be shadowed because it matches the same application as policy1.

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.

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

Transit traffic is defined as traffic that passesthroughthe SRX (not destined to the Routing Engine). To capture transit traffic:

Sampling and port mirroring (Option D)are the correct supported methods for capturing or exporting transit traffic. Sampling allows captured packets to be sent to a file or collector, while port mirroring sends a copy to a monitoring interface.

Option A:Firewall filters on an egress interface cannot directly capture packets; they can only count, accept, discard, or sample. Sampling itself is separate.

Option B:Loopback interface (lo0) is for control-plane traffic, not transit traffic.

Option C:tcpdump is not supported on SRX as a tool for capturing transit packets; the operational command monitor traffic interface is used, but sampling/port mirroring is the recommended scalable approach.

Correct Method:Sampling and port mirroring

Juniper SRX evaluatessecurity policiessequentially from top to bottom. Once a policy match is found, no further policies are evaluated. In this exhibit:

First Policy (FTP, deny):

Source: 172.25.11.0/24

Destination: 10.1.0.0/16

Application: FTP

Action: deny⇒Any FTP traffic from 172.25.11.0/24 to 10.1.0.0/16 isdenied.

Second Policy (SSH, permit):

Same source/destination but application = SSH

Action = permit⇒SSH traffic from 172.25.11.0/24 to 10.1.0.0/16 ispermitted.

Third Policy (HTTPS, permit):⇒HTTPS from the same source/destination ispermitted.

Fourth Policy (Ping, permit):

Source: 172.25.11.0/24 to any destination

Application: ping

Action: permit⇒ICMP echo requests (ping) from 172.25.11.0/24 to any destination arepermitted.

Fifth Policy (any → any, deny):⇒Serves as a defaultdeny allat the end.

Now checking each option:

Option A:SSH from 172.25.11.10 → 10.1.0.10 matches theSSH permit rule(second policy).✅Correct.

Option B:Ping from 172.25.11.100 → 10.1.0.10 matches theping permit rule(fourth policy). This traffic is permitted, not denied.❌Incorrect.

Option C:FTP from 10.1.0.10 → 172.25.11.100 isreverse traffic (untrust to trust). The table applies onlytrust → untrust, so this policy does not apply.❌Incorrect.

Option D:FTP from 172.25.11.11 → 10.1.0.10 matches the first policy (FTP deny rule).✅Correct.

Correct Statements:A, D

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