JNCIA-JUNOS Practice Test 2 — 10 Questions

Question 1

You are managing a small enterprise network with one Juniper router and two switches. The router connects to an ISP via ge-0/0/0 and to the internal network via ge-0/0/1. The internal network uses the 192.168.1.0/24 subnet. You need to configure a default route on the router to send all Internet-bound traffic to the ISP gateway at 203.0.113.1. You also want to ensure that internal hosts can reach the Internet. After configuring the default route, you test connectivity from a host on the internal network to an external website, but the ping fails. You verify that the host has an IP address of 192.168.1.100/24 and a default gateway of 192.168.1.1 (the router's internal interface). On the router, you run 'show route 0.0.0.0/0' and see the default route active. You also run 'ping 203.0.113.1' from the router and it succeeds. However, pinging from the host to the ISP gateway fails. What is the most likely cause?

Accepted Answer

Proxy ARP is not enabled on the router's internal interface.. Option D is correct because the host's default gateway (192.168.1.1) is correctly configured, and the router has a working default route to the ISP gateway (203.0.113.1). However, when the host sends a ping to an external IP (e.g., the ISP gateway), the router receives the packet on ge-0/0/1 and routes it out ge-0/0/0. The reply from 203.0.113.1 arrives back at the router's ge-0/0/0, but the router does not have a route for the host's source IP (192.168.1.100) in its routing table (since it's directly connected to ge-0/0/1, but the router needs to send an ARP request for that IP on ge-0/0/1). If Proxy ARP is not enabled on ge-0/0/1, the router will not respond to ARP requests for the host's IP, so the reply packet cannot be delivered to the host. Proxy ARP allows the router to answer ARP requests on behalf of hosts that are not on the same subnet, which is necessary here because the ISP gateway's reply is destined to 192.168.1.100, and the router must act as a proxy to forward that reply to the correct host.

Answer

DNS resolution is failing on the host.

Answer

The host's default gateway is incorrectly configured.

Answer

The default route is not active on the router.

Question 2

Which TWO statements correctly describe Junos configuration hierarchy and management?

Accepted Answer

The 'load merge' command imports configuration from a file and merges it with the current candidate configuration.. Option B is correct because the 'load merge' command in Junos imports configuration data from a file and merges it with the current candidate configuration, preserving existing statements unless explicitly overridden. This allows incremental changes without replacing the entire configuration, which is essential for efficient network operations.

Answer

The 'deactivate' command permanently removes a configuration statement from the candidate.

Answer

The 'set' command in configuration mode directly modifies the active configuration.

Answer

In operational mode, the 'show' command displays the candidate configuration.

Question 3

Which TWO statements correctly describe the behavior of the Junos CLI operational mode?

Accepted Answer

Commands such as show and ping are available.. Option A is correct because Junos CLI operational mode provides commands for monitoring, troubleshooting, and verifying the device state, such as 'show' for displaying configuration and operational data, and 'ping' for network connectivity tests. These commands do not alter the active configuration, which is the defining characteristic of operational mode.

Answer

Command options are enclosed in curly braces { }.

Answer

Commands must be entered in full; abbreviation is not allowed.

Answer

You can commit configuration changes directly.

Question 4

An engineer needs to apply a configuration change to the Junos device that must survive a reboot. Which configuration mode command should be used to save the changes?

Accepted Answer

commit. The 'commit' command is the standard way to apply a candidate configuration to the active configuration in Junos. When you issue 'commit', the changes are saved to the /config/juniper.conf.gz file, which is loaded upon reboot, ensuring the configuration survives a restart.

Answer

commit confirmed

Answer

commit synchronize

Answer

commit check

Question 5

Your company operates a dual-homed network with two Juniper MX routers (R1 and R2) each connected to a different ISP. R1 uses BGP to receive a default route from ISP-A (preference 170), and R2 uses BGP to receive a default route from ISP-B (preference 170). Additionally, both routers have a static default route pointing to a local next-hop (192.0.2.1) with preference 5 for backup. R1 and R2 are connected via an internal link (10.0.0.0/30) and run OSPF to exchange internal routes. You notice that traffic from internal hosts is always exiting via R1's ISP-A link, even when R1's BGP session to ISP-A goes down. The OSPF routes are preferred. You want traffic to fail over to R2's ISP-B link when R1 loses its BGP default. Which configuration change should you make?

Accepted Answer

Configure the static default route with a preference of 180 so that the BGP default routes (pref 170) are preferred when available.. Option D is correct because the static default route currently has a preference of 5, making it preferred over the BGP default (preference 170) even when the BGP route is available. By raising the static default's preference to 180 (higher than BGP's 170), the BGP default will be chosen when present, and the static default will only be used as a backup when BGP is unavailable. This ensures traffic fails over to R2's ISP-B link when R1 loses its BGP default, as OSPF will propagate the default from R2.

Answer

Increase the preference of the BGP default routes to 180 so that the static default is always preferred.

Answer

Configure a routing policy on R2 to reject the default route from ISP-B, forcing all traffic through R1.

Answer

Remove the static default route and rely on OSPF to propagate a default route from the router with the active BGP session.

Question 6

Match each Junos system log severity level to its meaning.

Question 7

Which THREE statements are true about commit operations in Junos OS?

Accepted Answer

Multiple users can make configuration changes simultaneously, but only one can commit at a time.. Option B is correct because Junos OS allows multiple users to enter configuration mode and make changes simultaneously, but the commit operation is serialized: only one user can commit at a time. This prevents conflicting changes from being applied concurrently, ensuring configuration consistency.

Answer

The 'commit confirmed' command immediately discards changes if not confirmed.

Answer

The 'commit' command always requires 'commit synchronize' when using dual Routing Engines.

Question 8

A network engineer is troubleshooting connectivity between two directly connected Juniper routers. The interface on Router A shows 'up' but no packets are being received from Router B. Which command should the engineer use on Router A to check if the interface is expecting to receive a specific encapsulation type?

Accepted Answer

show interfaces terse. Option B is correct because the 'show interfaces terse' command displays a concise summary of interface status, including the encapsulation type configured on each interface. If Router A expects a specific encapsulation (e.g., PPP, HDLC, or Ethernet) that does not match what Router B is sending, the interface will show 'up' but will not receive packets. This command allows the engineer to quickly verify the configured encapsulation type without extraneous details.

Answer

show interfaces extensive

Answer

show configuration interfaces

Answer

monitor traffic interface

Question 9

A network administrator is configuring a new subnet for servers that must not communicate with each other directly but must be able to reach a default gateway. Which type of route should be configured on the servers?

Accepted Answer

Default route pointing to the gateway. A default route (0.0.0.0/0) pointing to the gateway is correct because it allows servers to reach any external destination (including the gateway) without requiring explicit routes to each other. Since the servers must not communicate directly, they should not have routes to each other's subnets; the default route ensures all non-local traffic is forwarded to the gateway, which can then enforce isolation policies.

Answer

Host route for the gateway

Answer

Dynamic route via OSPF

Answer

Static route to each other server

Question 10

An engineer is designing a network with two routers connected via a serial link. The link should support multiple logical subinterfaces for different VLANs. Which encapsulation type must be used on the serial interface?

Accepted Answer

Frame Relay. Frame Relay is correct because it supports multiple logical subinterfaces (DLCIs) on a single serial link, allowing different VLANs to be mapped to separate virtual circuits. Unlike PPP or HDLC, Frame Relay inherently provides the ability to create point-to-point or multipoint subinterfaces for Layer 2 segmentation.

Answer

Ethernet

Answer

PPP

Answer

HDLC