Networking Fundamentals

An administrator needs to ensure that traffic from the 192.168.1.0/24 subnet is allowed to reach the internet through a Juniper SRX firewall. The SRX is configured with security policies. Which policy element is required to permit this traffic?

Question 3hardmulti select

Open the full BGP breakdown →

Which TWO statements about Juniper's implementation of static routes are correct? (Choose two.)

Question 4hardmultiple choice

You are responsible for a Juniper MX router that connects two customer sites over a Layer 3 VPN. The router is configured with BGP for VPN routes and uses MPLS to forward traffic. Recently, the customer reported that traffic from Site A (10.0.1.0/24) to Site B (10.0.2.0/24) is intermittently failing. You check the routing table on the router and see that both routes are present with valid next-hops. However, when you ping from the router's loopback to the remote site's loopback, the ping succeeds. MPLS labels are being assigned and the LSP is up. You also notice that when the failure occurs, the router's BGP session to the remote PE is still established. The failure seems random and lasts a few seconds before recovering. Which troubleshooting step is most likely to identify the root cause?

Question 5hardmultiple choice

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?

Question 6mediummatching

Match each Junos system log severity level to its meaning.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

System is unusable

Immediate action needed

Critical conditions

Error conditions

Warning conditions

Question 7mediummultiple choice

A Juniper EX switch has two VLANs configured, each with an IRB interface assigned an IP address. Pings between hosts in different VLANs fail. What is the most likely missing configuration?

Question 8mediummultiple choice

Refer to the exhibit. A packet with destination IP 192.168.1.100 arrives. Which next-hop IP will the router use?

Exhibit

inet.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
0.0.0.0/0          *[Static/5] 00:00:01 > to 10.0.0.1 via ge-0/0/0.0
10.0.0.0/8         *[Direct/0] 00:00:01 > via ge-0/0/0.0
10.0.0.1/32        *[Local/0] 00:00:01 Local via ge-0/0/0.0
192.168.1.0/24     *[Static/5] 00:00:01 > to 10.0.0.2 via ge-0/0/0.0

Question 9easymultiple choice

An engineer is troubleshooting a network issue where hosts on the same VLAN cannot communicate with each other. Which configuration element is most likely missing?

Question 10easymultiple choice

A network administrator is configuring a new OSPF network. Which statement about OSPF router IDs is correct?

Question 11mediummultiple choice

A network administrator is implementing OSPF on a Juniper MX router. During verification, the OSPF adjacency does not come up. The interfaces have correct IP addresses and are up. What is the most likely cause?

Question 12mediummulti select

Which THREE factors influence OSPF neighbor adjacency formation? (Choose three.)

Question 13hardmulti select

Which THREE are valid methods to reduce spanning-tree convergence time? (Choose three.)

Question 14hardmultiple choice

You are a network engineer for a large enterprise deploying a new data center using a spine-and-leaf architecture with Juniper QFX5100 switches. The underlay network uses OSPF for loopback reachability, and the overlay uses EBGP for EVPN. The leaf switches are configured as VTEPs (Virtual Tunnel Endpoints). One of the leaf switches, leaf-03, cannot establish OSPF adjacency with its spine switch, spine-01. The interfaces are up/up and the IP addresses are correctly configured. 'show ospf neighbor' on leaf-03 returns nothing. 'show ospf interface' shows the interface is in state DOWN. Both switches are configured with the same OSPF area (0.0.0.0) and the same hello interval (10 seconds). The MTU on both sides is 1500. Authentication is not configured. The spine switch has multiple OSPF neighbors from other leaves. The network is in production and other leaf switches are working fine. What is the most likely cause of the problem?

Question 15hardmultiple choice

Refer to the exhibit. The administrator has verified that the remote router's interface uses PPP encapsulation. What is the most likely cause of the link not passing traffic?

Exhibit

root> show interfaces ge-0/0/0 | match "Physical"
  Physical interface: ge-0/0/0, Enabled, Physical link is Up
  Link layer protocol: HDLC

Question 16easymultiple choice

You are troubleshooting a Juniper EX switch. A host connected to interface ge-0/0/5 is sending frames, but the switch is not learning its MAC address in the correct VLAN. You verify that the interface is up and configured as an access port in VLAN 10. Which action should you take to allow the switch to learn the MAC address?

Question 17mediummultiple choice

A network administrator notices that traffic between two VLANs is not reaching its destination. The switch has an IRB interface configured with an IP address in each VLAN's subnet. What is the most likely missing configuration?

Question 18hardmultiple choice

A network engineer is troubleshooting OSPF adjacencies between two Juniper routers. The routers are directly connected and have matching OSPF configurations except for the router IDs. Router A has router-id 10.0.0.1, Router B has router-id 10.0.0.2. The adjacency remains in the EXSTART state. What is the most likely cause?

Question 19mediummultiple choice

A network engineer is designing a redundant network with two Juniper routers running VRRP. The virtual IP address is 10.0.0.1. Both routers are configured as VRRP group 1. What is the purpose of the 'priority' parameter in VRRP configuration?

Question 20mediummultiple choice

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?

Question 21easymultiple choice

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?

Question 22mediummultiple choice

Read the full VPN explanation →

A Juniper router is configured with two static routes to the same destination network, both with the same preference. One route has a metric of 5, the other a metric of 10. Which route will be installed in the routing table?

Question 23mediumdrag order

Arrange the steps to configure an IPsec VPN on a Junos SRX in the correct order.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 24easymultiple choice

A network engineer is troubleshooting connectivity between two hosts on the same VLAN connected to different Juniper EX switches. The MAC address table on each switch shows the correct MAC addresses for both hosts, but ping fails. What is the most likely cause?

Question 25easymultiple choice

A host needs to verify that its assigned IP address is not already in use on the network. Which type of packet does the host send?

Question 26mediummultiple choice

A router receives a packet with destination IP 10.1.1.100. The routing table contains two entries: a static route to 10.1.1.0/24 via 192.168.1.1, and an OSPF route to 10.1.1.0/25 via 192.168.2.1. Which route will the router use?

Question 27hardmultiple choice

Open the full STP breakdown →

A host in VLAN 10 can ping a host in VLAN 20 without a default gateway configured. What feature is likely enabled on the router that interconnects the VLANs?

Question 28hardmultiple choice

An engineer enables Spanning Tree PortFast on a switch port connected to a host. Later, another switch is connected to that same port, causing a loop. What feature could have prevented this?

Question 29easymultiple choice

A switch receives a unicast frame with a destination MAC address that is present in its MAC address table. How does the switch process the frame?

Question 30mediummultiple choice

Which field in an Ethernet frame is used by a switch to learn which source MAC address belongs to which port?

Question 31hardmultiple choice

Full Practice Test →All Objectives

Two routers are connected via a point-to-point Ethernet link. They are configured with IP addresses in the same subnet, but OSPF does not form an adjacency. The link is up/up. What is a likely cause?

More Networking Fundamentals questions available in the full practice test.

Continue Practising →

All JN0-106 Objectives

Objective 1.016% of exam

Networking Fundamentals

JN0-106 Practice Questions

What this objective tests

JN0-106 Networking Fundamentals — Key Topics

Mapping protocols like ARP, ICMP, TCP and UDP to OSI and TCP/IP layers
IPv4 addressing, subnet masks, CIDR notation and host/network range calculation
Junos interface naming and status shown by show interfaces terse
Ethernet concepts including MAC addressing, frames, and collision/broadcast domains

Common exam traps

Where candidates lose marks on Networking Fundamentals

⚠Confusing OSI layer numbers with TCP/IP layers, for example placing ARP at Layer 3 instead of Layer 2
⚠Calculating usable hosts by forgetting to subtract the network and broadcast addresses from 2^n
⚠Assuming a Junos interface is up when show interfaces terse shows only the link up but protocol down

JN0-106 Networking Fundamentals — Practice Questions

30 questions from this objective · 16% of your JN0-106 exam

Question 2easymultiple choice

An administrator needs to ensure that traffic from the 192.168.1.0/24 subnet is allowed to reach the internet through a Juniper SRX firewall. The SRX is configured with security policies. Which policy element is required to permit this traffic?

Question 3hardmulti select

Open the full BGP breakdown →

Which TWO statements about Juniper's implementation of static routes are correct? (Choose two.)

Question 4hardmultiple choice

You are responsible for a Juniper MX router that connects two customer sites over a Layer 3 VPN. The router is configured with BGP for VPN routes and uses MPLS to forward traffic. Recently, the customer reported that traffic from Site A (10.0.1.0/24) to Site B (10.0.2.0/24) is intermittently failing. You check the routing table on the router and see that both routes are present with valid next-hops. However, when you ping from the router's loopback to the remote site's loopback, the ping succeeds. MPLS labels are being assigned and the LSP is up. You also notice that when the failure occurs, the router's BGP session to the remote PE is still established. The failure seems random and lasts a few seconds before recovering. Which troubleshooting step is most likely to identify the root cause?

Question 5hardmultiple choice

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?

Question 6mediummatching

Match each Junos system log severity level to its meaning.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts

Matches

System is unusable

Immediate action needed

Critical conditions

Error conditions

Warning conditions

Question 7mediummultiple choice

A Juniper EX switch has two VLANs configured, each with an IRB interface assigned an IP address. Pings between hosts in different VLANs fail. What is the most likely missing configuration?

Question 8mediummultiple choice

Refer to the exhibit. A packet with destination IP 192.168.1.100 arrives. Which next-hop IP will the router use?

Exhibit

inet.0: 4 destinations, 4 routes (4 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
0.0.0.0/0          *[Static/5] 00:00:01 > to 10.0.0.1 via ge-0/0/0.0
10.0.0.0/8         *[Direct/0] 00:00:01 > via ge-0/0/0.0
10.0.0.1/32        *[Local/0] 00:00:01 Local via ge-0/0/0.0
192.168.1.0/24     *[Static/5] 00:00:01 > to 10.0.0.2 via ge-0/0/0.0

Question 9easymultiple choice

An engineer is troubleshooting a network issue where hosts on the same VLAN cannot communicate with each other. Which configuration element is most likely missing?

Question 10easymultiple choice

A network administrator is configuring a new OSPF network. Which statement about OSPF router IDs is correct?

Question 11mediummultiple choice

A network administrator is implementing OSPF on a Juniper MX router. During verification, the OSPF adjacency does not come up. The interfaces have correct IP addresses and are up. What is the most likely cause?

Question 12mediummulti select

Which THREE factors influence OSPF neighbor adjacency formation? (Choose three.)

Question 13hardmulti select

Which THREE are valid methods to reduce spanning-tree convergence time? (Choose three.)

Question 14hardmultiple choice

You are a network engineer for a large enterprise deploying a new data center using a spine-and-leaf architecture with Juniper QFX5100 switches. The underlay network uses OSPF for loopback reachability, and the overlay uses EBGP for EVPN. The leaf switches are configured as VTEPs (Virtual Tunnel Endpoints). One of the leaf switches, leaf-03, cannot establish OSPF adjacency with its spine switch, spine-01. The interfaces are up/up and the IP addresses are correctly configured. 'show ospf neighbor' on leaf-03 returns nothing. 'show ospf interface' shows the interface is in state DOWN. Both switches are configured with the same OSPF area (0.0.0.0) and the same hello interval (10 seconds). The MTU on both sides is 1500. Authentication is not configured. The spine switch has multiple OSPF neighbors from other leaves. The network is in production and other leaf switches are working fine. What is the most likely cause of the problem?

Question 15hardmultiple choice

Refer to the exhibit. The administrator has verified that the remote router's interface uses PPP encapsulation. What is the most likely cause of the link not passing traffic?

Exhibit

root> show interfaces ge-0/0/0 | match "Physical"
  Physical interface: ge-0/0/0, Enabled, Physical link is Up
  Link layer protocol: HDLC

Question 16easymultiple choice

You are troubleshooting a Juniper EX switch. A host connected to interface ge-0/0/5 is sending frames, but the switch is not learning its MAC address in the correct VLAN. You verify that the interface is up and configured as an access port in VLAN 10. Which action should you take to allow the switch to learn the MAC address?

Question 17mediummultiple choice

A network administrator notices that traffic between two VLANs is not reaching its destination. The switch has an IRB interface configured with an IP address in each VLAN's subnet. What is the most likely missing configuration?

Question 18hardmultiple choice

A network engineer is troubleshooting OSPF adjacencies between two Juniper routers. The routers are directly connected and have matching OSPF configurations except for the router IDs. Router A has router-id 10.0.0.1, Router B has router-id 10.0.0.2. The adjacency remains in the EXSTART state. What is the most likely cause?

Question 19mediummultiple choice

A network engineer is designing a redundant network with two Juniper routers running VRRP. The virtual IP address is 10.0.0.1. Both routers are configured as VRRP group 1. What is the purpose of the 'priority' parameter in VRRP configuration?

Question 20mediummultiple choice

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?

Question 21easymultiple choice

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?

Question 22mediummultiple choice

Read the full VPN explanation →

A Juniper router is configured with two static routes to the same destination network, both with the same preference. One route has a metric of 5, the other a metric of 10. Which route will be installed in the routing table?

Question 23mediumdrag order

Arrange the steps to configure an IPsec VPN on a Junos SRX in the correct order.

Drag or tap steps into the slots.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 24easymultiple choice

A network engineer is troubleshooting connectivity between two hosts on the same VLAN connected to different Juniper EX switches. The MAC address table on each switch shows the correct MAC addresses for both hosts, but ping fails. What is the most likely cause?

Question 25easymultiple choice

A host needs to verify that its assigned IP address is not already in use on the network. Which type of packet does the host send?

Question 26mediummultiple choice

A router receives a packet with destination IP 10.1.1.100. The routing table contains two entries: a static route to 10.1.1.0/24 via 192.168.1.1, and an OSPF route to 10.1.1.0/25 via 192.168.2.1. Which route will the router use?

Question 27hardmultiple choice

Open the full STP breakdown →

A host in VLAN 10 can ping a host in VLAN 20 without a default gateway configured. What feature is likely enabled on the router that interconnects the VLANs?

Question 28hardmultiple choice

An engineer enables Spanning Tree PortFast on a switch port connected to a host. Later, another switch is connected to that same port, causing a loop. What feature could have prevented this?

Question 29easymultiple choice

A switch receives a unicast frame with a destination MAC address that is present in its MAC address table. How does the switch process the frame?

Question 30mediummultiple choice

Which field in an Ethernet frame is used by a switch to learn which source MAC address belongs to which port?

Question 31hardmultiple choice