JNCIA-SEC Practice Test 5 — 25 Questions

Question 1

You suspect that asymmetrical routing is causing packets to be dropped by the Junos security session handler. Which command allows you to view detailed session information, including the expected and received packet direction and interface?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

show security flow session detail. The show security flow session detail command provides comprehensive information about a session, including incoming and outgoing interfaces, translated addresses, and packet counts.

Answer

show security flow session summary

Answer

show security flow node 0 session

Answer

show security flow session interface

Question 2

While analyzing packet flow using security flow traceoptions, you see the message: "ALG: and AlgOpen() failed". What does this indicate?

Accepted Answer

The Application Layer Gateway failed to allocate necessary resources or set up dynamic data channels.. Application Layer Gateways (ALGs) handle complex protocols like FTP, SIP, or TFTP. An AlgOpen() failure means the specific ALG failed to allocate resources or open secondary dynamic pinholes.

Answer

The primary security policy denied the initial control connection.

Answer

The NAT pool was exhausted during source translation.

Answer

The destination host refused the TCP connection via a RST packet.

Question 3

Which TWO logs or log categories can an administrator examine to troubleshoot security policy actions such as permits and denies? (Choose two)

Accepted Answer

RT_FLOW session initiation and close logs (RT_FLOW_SESSION_INIT / RT_FLOW_SESSION_CLOSE). Security policy actions are recorded in RT_FLOW syslog messages and can be viewed via local log files or external SIEMs.

Answer

Routing protocol daemon (rpd) logs

Answer

Chassis environmental logs

Answer

System kernel boot logs

Question 4

Which Junos configuration hierarchy is used to define Destination NAT rule-sets?

Accepted Answer

set security nat destination rule-set. Destination NAT rule-sets are configured under the 'security nat destination rule-set' hierarchy.

Answer

set security policies destination-nat

Answer

set security nat rule-set destination

Answer

set security nat-policy destination

Question 5

Which Junos configuration statement defines the match criteria for source address within a Source NAT rule?

Accepted Answer

match source-address 192.168.1.0/24. Source NAT rules specify match criteria using 'match source-address <ip-prefix>' within the rule hierarchy.

Answer

address source 192.168.1.0/24

Answer

from source 192.168.1.0/24

Answer

source-address-match 192.168.1.0/24

Question 6

Which TWO commands can be used to view IDP configuration status and threat detection statistics? (Choose two)

Accepted Answer

show security idp status. IDP status and stats are viewed using security idp operational commands.

Answer

show firewall idp-counters

Answer

show security flow idp-status

Answer

show system idp-status

Question 7

Which TWO statements are correct regarding the evaluation order and behavior of NAT in Junos OS? (Choose two)

Accepted Answer

Destination NAT is evaluated before Source NAT.. Junos evaluates Destination NAT first and Static NAT last. Rules within rule-sets are evaluated top-down.

Answer

Source NAT rule-sets ignore source zones during packet processing.

Answer

All NAT rules are evaluated simultaneously using longest-prefix matching.

Answer

Static NAT is evaluated before Destination NAT.

Question 8

A network engineer implements pool-based Source NAT with Port Address Translation (PAT) on a Junos OS device using a pool containing a single public IP address. After deployment, users in the trust zone experience intermittent failures when opening numerous concurrent browser tabs to various internet sites. 'show security flow session' reveals many sessions in a closing state. What is the root cause?

Accepted Answer

Port exhaustion has occurred because all available source ports for the single translation IP are in use.. Port exhaustion occurs when a single IP address runs out of available source ports (totaling 65,535, though ephemeral ports are usually a subset like 1024-65535). Heavy concurrent browser usage quickly exhausts these ports.

Answer

The security policy action is set to permit instead of translating, causing port reuse collisions.

Answer

The source NAT pool lacks the 'port-overloading' statement, causing the device to drop excess traffic.

Answer

Junos OS requires an explicit maximum-sessions limit per pool address to prevent CPU overload.

Question 9

Which Junos operational command allows an administrator to view translation statistics and hit counts for NAT rule sets?

Accepted Answer

show security nat rule-set. To check hit counts and statistics for NAT rule sets and rules, the command 'show security nat rule-set' is used.

Answer

show security flow statistics nat

Answer

show system services nat statistics

Answer

show nat summary counters

Question 10

Which Junos configuration command correctly establishes a destination NAT pool pointing to an internal server IP address of 10.2.2.50?

Accepted Answer

set security nat destination pool srv-pool address 10.2.2.50/32. Destination NAT pools are defined under 'security nat destination pool address '.

Answer

set security nat destination address-pool srv-pool 10.2.2.50

Answer

set security nat pool destination srv-pool 10.2.2.50

Answer

set security nat destination rule-set rs1 pool srv-pool address 10.2.2.50

Question 11

Which THREE actions are effective when diagnosing intermittent connectivity issues through an SRX firewall where asymmetric routing is suspected? (Choose three)

Accepted Answer

Inspect active sessions using 'show security flow session' to verify session state progression. Asymmetric routing troubleshooting involves flow traceoptions, session table inspection, and disabling SYN checks if necessary.

Answer

Reconfigure all firewall security policies to permit any-to-any traffic

Answer

Restart the device chassis power supplies

Question 12

An administrator needs to monitor CPU and memory utilization of the Routing Engine and Forwarding Plane on an SRX device. Which command provides this hardware health overview?

Accepted Answer

show system resources. The show system statistics or show chassis routing-engine commands display CPU and memory health, but show system resources provides a quick snapshot of system processes.

Answer

show chassis hardware

Answer

show security flow status

Answer

show security monitoring resources

Question 13

An administrator needs to verify whether ALG (Application Layer Gateway) for FTP is currently enabled and active on an SRX device. Which command should be used?

Accepted Answer

show security alg status. ALG status and statistics can be verified using the show security alg status command.

Answer

show security alg ftp statistics

Answer

show system alg

Answer

show security flow alg

Question 14

During packet flow troubleshooting on an SRX Series device, an administrator uses security flow traceoptions with the flag 'packet'. What potential impact should the administrator be aware of before enabling this on a high-throughput production device?

Accepted Answer

It can cause high CPU utilization and rapidly fill up log storage due to massive logging volume.. Enabling packet-level tracing in flow traceoptions causes high CPU utilization and log file bloat due to the massive volume of captured packets.

Answer

It drops all transit traffic matching the trace filter.

Answer

It forces the device to reboot into single-user recovery mode.

Answer

It automatically disables all active security policies on the device.

Question 15

Which TWO statements describe the behavior of Static NAT on Junos OS devices? (Choose two)

Accepted Answer

It provides a one-to-one mapping between a public IP address and a private IP address.. Static NAT provides a 1:1 mapping between public and private IPs and is inherently bidirectional.

Answer

It requires interface-based NAT to function on external ports.

Answer

It requires port overloading (PAT) to share a single public IP among multiple hosts.

Answer

It is evaluated before Destination NAT in the Junos NAT processing order.

Question 16

You have configured Destination NAT on a SRX Series device to forward web traffic to an internal server. External clients attempt to connect, but the security logs show sessions are being dropped by the security policy. Which security zone and IP address combination must the security policy permit?

Accepted Answer

From the untrusted zone to the trusted zone, using the internal private IP address of the server.. Junos OS security policies for Destination NAT evaluate traffic based on the *post-translation* destination IP address (the internal server's private IP) and the zone where the internal server resides.

Answer

From the untrusted zone to the untrusted zone, using the public destination IP address.

Answer

From the untrusted zone to the trusted zone, using the pre-translation public IP address.

Answer

From the trusted zone to the untrusted zone, using the public destination IP address.

Question 17

While investigating an issue where an IPsec VPN tunnel fails to pass data traffic, which THREE commands should you execute to verify Phase 1, Phase 2, and security associations? (Choose three)

Accepted Answer

show security ipsec security-associations. To troubleshoot IPsec VPNs thoroughly, you must check IKE SAs (Phase 1), IPsec SAs (Phase 2), and IPsec statistics.

Answer

show security alg status

Answer

show security flow session summary

Question 18

Which configuration statement correctly defines a source NAT pool named 'corp-pool' with an address range from 203.0.113.10 to 203.0.113.20 on Junos OS?

Accepted Answer

set security nat source pool corp-pool address 203.0.113.10 to 203.0.113.20. Source NAT pools are configured under 'security nat source pool address ' using Junos CLI syntax.

Answer

set security nat source pool corp-pool address 203.0.113.10/32 to 203.0.113.20/32

Answer

set security nat source address-pool corp-pool range 203.0.113.10-203.0.113.20

Answer

set security nat source pool corp-pool address 203.0.113.10/28

Question 19

An administrator is troubleshooting a policy drop issue using security flow traceoptions. Which THREE configuration elements are required to successfully generate trace output? (Choose three)

Accepted Answer

Configure match criteria (such as source-ip or destination-ip) to isolate specific traffic.. Configuring traceoptions requires specifying a file name, setting the appropriate debug flags, and defining match criteria to isolate the traffic.

Answer

Set the security policy action to 'reject' for the targeted traffic.

Answer

Enable kernel-level debugging via the FreeBSD shell.

Question 20

An administrator suspects that asymmetric routing is disrupting traffic flow through an SRX Series device. Which THREE symptoms or diagnostic indicators point toward asymmetric routing? (Choose three)

Accepted Answer

Flow traceoptions show drops with reasons such as "No session found" or reverse path validation failures.. Asymmetric routing causes session creation failures, reverse flow mismatches, and specific flow trace drop messages.

Answer

The chassis cluster fails over immediately.

Answer

CPU utilization on the Routing Engine spikes to 100%.