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JUNIPER NETWORKS CERTIFIED
ASSOCIATE – JUNOS (JNCIA-JUNOS)
PRACTICE EXAM 2026/2027 QUESTIONS
WITH VERIFIED ANSWERS & COMPLETE
RATIONALES
**1. A network administrator is designing a new LAN topology
for a branch office. They are deploying a 24-port Layer 2
Ethernet switch to connect workstations and a single router to
connect the branch to the corporate WAN. How many
broadcast domains and collision domains exist in this topology
assuming all 24 switch ports are connected to active
workstations and one port connects to the router?**
A. 1 broadcast domain, 1 collision domain
B. 1 broadcast domain, 24 collision domains
C. 1 broadcast domain, 25 collision domains
D. 25 broadcast domains, 25 collision domains
**Correct answer:** C
**Rationale:** A Layer 2 switch creates a single broadcast
domain for all connected devices (unless VLANs are
configured) but isolates collision domains per port. With 24
workstations and 1 router connected to the switch, there are 25
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active switch ports, resulting in 25 separate collision domains
operating within 1 broadcast domain .
---
**2. A Junos device receives a packet destined for the IP
address 10.1.5.50. The routing table contains multiple active
routes that encompass this destination. Based on the longest
match routing principle, which of the following routes will the
router select to forward the packet?**
A. 10.0.0.0/8
B. 10.1.0.0/16
C. 10.1.5.0/24
D. 0.0.0.0/0
**Correct answer:** C
**Rationale:** Routers use the longest prefix match algorithm to
select the best route among overlapping subnets. The route
with the longest subnet mask (highest number of network bits)
is the most specific. Among /8, /16, /24, and /0, the /24 route is
the most specific match for 10.1.5.50 .
---
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**3. Which statement is true about the internal link between the
Routing Engine and the Packet Forwarding Engine in Junos
OS?**
A. It is only used for exception traffic
B. It is an FE link called fxp2
C. It is rate limited to avoid DDoS attacks
D. It is only used to send the forwarding table from the Routing
Engine to the Packet Forwarding Engine
**Correct answer:** C
**Rationale:** The internal link between the Routing Engine and
Packet Forwarding Engine is rate limited to protect against
denial-of-service attacks. This link carries exception traffic
(traffic destined for the Routing Engine) and is designed with
protection mechanisms to prevent overwhelming the control
plane .
---
**4. What is an internal interface in Junos OS?**
A. An interface used to connect the control and forwarding
planes
B. An interface used for user traffic
JUNIPER NETWORKS CERTIFIED
ASSOCIATE – JUNOS (JNCIA-JUNOS)
PRACTICE EXAM 2026/2027 QUESTIONS
WITH VERIFIED ANSWERS & COMPLETE
RATIONALES
**1. A network administrator is designing a new LAN topology
for a branch office. They are deploying a 24-port Layer 2
Ethernet switch to connect workstations and a single router to
connect the branch to the corporate WAN. How many
broadcast domains and collision domains exist in this topology
assuming all 24 switch ports are connected to active
workstations and one port connects to the router?**
A. 1 broadcast domain, 1 collision domain
B. 1 broadcast domain, 24 collision domains
C. 1 broadcast domain, 25 collision domains
D. 25 broadcast domains, 25 collision domains
**Correct answer:** C
**Rationale:** A Layer 2 switch creates a single broadcast
domain for all connected devices (unless VLANs are
configured) but isolates collision domains per port. With 24
workstations and 1 router connected to the switch, there are 25
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active switch ports, resulting in 25 separate collision domains
operating within 1 broadcast domain .
---
**2. A Junos device receives a packet destined for the IP
address 10.1.5.50. The routing table contains multiple active
routes that encompass this destination. Based on the longest
match routing principle, which of the following routes will the
router select to forward the packet?**
A. 10.0.0.0/8
B. 10.1.0.0/16
C. 10.1.5.0/24
D. 0.0.0.0/0
**Correct answer:** C
**Rationale:** Routers use the longest prefix match algorithm to
select the best route among overlapping subnets. The route
with the longest subnet mask (highest number of network bits)
is the most specific. Among /8, /16, /24, and /0, the /24 route is
the most specific match for 10.1.5.50 .
---
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**3. Which statement is true about the internal link between the
Routing Engine and the Packet Forwarding Engine in Junos
OS?**
A. It is only used for exception traffic
B. It is an FE link called fxp2
C. It is rate limited to avoid DDoS attacks
D. It is only used to send the forwarding table from the Routing
Engine to the Packet Forwarding Engine
**Correct answer:** C
**Rationale:** The internal link between the Routing Engine and
Packet Forwarding Engine is rate limited to protect against
denial-of-service attacks. This link carries exception traffic
(traffic destined for the Routing Engine) and is designed with
protection mechanisms to prevent overwhelming the control
plane .
---
**4. What is an internal interface in Junos OS?**
A. An interface used to connect the control and forwarding
planes
B. An interface used for user traffic
