Practice Free JN0-281 Exam Online Questions
Question #21
What is a VLAN?
- A . A local network using only virtual machines
- B . A broadcast domain, identified by a VLAN ID
- C . A multicast domain, identified by a VLAN ID
- D . A broadcast domain, using only virtual machines
Correct Answer: B
Question #22
Load balancing in routing is used to:
- A . Encrypt data packets.
- B . Distribute traffic evenly across multiple paths.
- C . Compress data to improve transmission speed.
- D . Automatically update routing tables.
Correct Answer: B
Question #23
Which of the following are functions of MACsec? (Choose two)
- A . It provides Layer 2 encryption.
- B . It prevents MAC flooding attacks.
- C . It offers data integrity and confidentiality.
- D . It enables VLAN tagging.
Correct Answer: AC
Question #24
Which Junos OS routing table stores IPv6 addresses?
- A . inet.0
- B . inet0.6
- C . inet.6
- D . inet6.0
Correct Answer: D
D
Explanation:
In Junos OS, routing information is stored in different routing tables depending on the protocol and address family. For IPv6 addresses, the routing table used is inet6.0.
Step-by-Step :
Routing Tables in Junos:
inet.0: This is the primary routing table for IPv4 unicast routes.
inet6.0: This is the primary routing table for IPv6 unicast routes.
inet.3: This routing table is used for MPLS-related routing.
Other routing tables, like inet.1, inet.2, are used for multicast and other specific purposes.
inet6.0 Routing Table:
When IPv6 is enabled on a Juniper router, all the IPv6 routes are stored in the inet6.0 table. This includes both direct routes (connected networks) and learned routes (from dynamic routing protocols like OSPFv3, BGP, etc.).
Verification:
To view IPv6 routes, the command show route table inet6.0 is used. This will display the contents of the IPv6 routing table, showing the network prefixes, next-hop addresses, and protocol information for each route.
Juniper
Reference: Junos Command: Use show route table inet6.0 to check IPv6 routing entries.
IPv6 Routing: Ensure that the IPv6 protocol is enabled on interfaces and that routing protocols like OSPFv3 or BGP are properly configured for IPv6 traffic handling.
D
Explanation:
In Junos OS, routing information is stored in different routing tables depending on the protocol and address family. For IPv6 addresses, the routing table used is inet6.0.
Step-by-Step :
Routing Tables in Junos:
inet.0: This is the primary routing table for IPv4 unicast routes.
inet6.0: This is the primary routing table for IPv6 unicast routes.
inet.3: This routing table is used for MPLS-related routing.
Other routing tables, like inet.1, inet.2, are used for multicast and other specific purposes.
inet6.0 Routing Table:
When IPv6 is enabled on a Juniper router, all the IPv6 routes are stored in the inet6.0 table. This includes both direct routes (connected networks) and learned routes (from dynamic routing protocols like OSPFv3, BGP, etc.).
Verification:
To view IPv6 routes, the command show route table inet6.0 is used. This will display the contents of the IPv6 routing table, showing the network prefixes, next-hop addresses, and protocol information for each route.
Juniper
Reference: Junos Command: Use show route table inet6.0 to check IPv6 routing entries.
IPv6 Routing: Ensure that the IPv6 protocol is enabled on interfaces and that routing protocols like OSPFv3 or BGP are properly configured for IPv6 traffic handling.
Question #25
What does the “qualified-next-hop” feature do when configuring a static route?
- A . It allows you to specify an independent route preference value for an additional next hop.
- B . It specifies the IP address of the directly connected device.
- C . It instructs the device to verify the next-hop is reachable before activating the route.
- D . It instructs the device to looks up a static route’s next-hop that is not directly connected.
Correct Answer: A
Question #26
You are troubleshooting a downed BGP session.
Referring to the exhibit, what is the cause of the problem?
- A . The UDP session between the peers has not been established.
- B . The local peer has sent an Open message but not received one from the remote peer.
- C . The TCP session between the peers has not been established.
- D . The local peer has sent an Update message but not received one from the remote peer.
Correct Answer: C
C
Explanation:
The BGP session in the exhibit shows the state as Connect, which indicates that the TCP session between the BGP peers has not been fully established. Step-by-Step Breakdown:
BGP State "Connect":
The Connect state is the second stage in the BGP finite state machine (FSM). At this stage, BGP is trying to establish a TCP session with the peer, but the session has not yet been successfully established.
A successful TCP three-way handshake (SYN, SYN-ACK, ACK) is required before BGP can progress to the OpenSent state, where the peers exchange BGP Open messages.
Possible Causes:
A firewall blocking TCP port 179.
Incorrect IP addresses or network connectivity issues between the BGP peers. Juniper
Reference: BGP Troubleshooting: In Junos, if a BGP session is stuck in the Connect state, the issue is likely due to a failure in establishing the underlying TCP connection.
C
Explanation:
The BGP session in the exhibit shows the state as Connect, which indicates that the TCP session between the BGP peers has not been fully established. Step-by-Step Breakdown:
BGP State "Connect":
The Connect state is the second stage in the BGP finite state machine (FSM). At this stage, BGP is trying to establish a TCP session with the peer, but the session has not yet been successfully established.
A successful TCP three-way handshake (SYN, SYN-ACK, ACK) is required before BGP can progress to the OpenSent state, where the peers exchange BGP Open messages.
Possible Causes:
A firewall blocking TCP port 179.
Incorrect IP addresses or network connectivity issues between the BGP peers. Juniper
Reference: BGP Troubleshooting: In Junos, if a BGP session is stuck in the Connect state, the issue is likely due to a failure in establishing the underlying TCP connection.
Question #27
What does filter-based forwarding in networking typically allow?
- A . Forwarding decisions based on MAC addresses
- B . Load balancing across multiple CPUs
- C . Routing decisions based on extended criteria like packet headers
- D . Aggregation of multiple routes into a single entry
Correct Answer: C
Question #28
Which three actions are required to implement filter-based forwarding? (Choose three.)
- A . You must create an instance-type forwarding routing instance.
- B . You must create an instance-type vrf routing instance.
- C . You must create a match filter.
- D . You must create a security policy.
- E . You must create a RIB group.
Correct Answer: A, C, E
A, C, E
Explanation:
Filter-Based Forwarding (FBF) in Junos OS allows traffic to be routed based on specific criteria such as source address, rather than just the destination address. This is useful in scenarios like policy routing or providing multiple paths for different types of traffic. Step-by-Step Breakdown:
Instance-Type Forwarding:
You must create an instance-type forwarding routing instance. This routing instance allows for different routing tables based on the incoming packet filter.
Command:
set routing-instances FBF-instance instance-type forwarding Match Filter:
You need to create a filter to match the traffic that will be forwarded according to your custom routing policy. This filter is applied to an interface to determine which traffic will use the custom forwarding instance.
Command Example:
set firewall family inet filter FBF-filter term 1 from source-address <address> set firewall family inet filter FBF-filter term 1 then routing-instance FBF-instance RIB Group:
A RIB (Routing Information Base) group is necessary to share routes between the primary routing table and the custom routing instance. This allows FBF traffic to use the routing information from other routing tables.
Command Example:
set routing-options rib-groups FBF-group import-rib inet.0
set routing-instances FBF-instance routing-options rib-group FBF-group
Juniper
Reference: FBF Configuration: Filter-based forwarding requires these specific steps to redirect traffic to a custom routing table based on filter criteria.
A, C, E
Explanation:
Filter-Based Forwarding (FBF) in Junos OS allows traffic to be routed based on specific criteria such as source address, rather than just the destination address. This is useful in scenarios like policy routing or providing multiple paths for different types of traffic. Step-by-Step Breakdown:
Instance-Type Forwarding:
You must create an instance-type forwarding routing instance. This routing instance allows for different routing tables based on the incoming packet filter.
Command:
set routing-instances FBF-instance instance-type forwarding Match Filter:
You need to create a filter to match the traffic that will be forwarded according to your custom routing policy. This filter is applied to an interface to determine which traffic will use the custom forwarding instance.
Command Example:
set firewall family inet filter FBF-filter term 1 from source-address <address> set firewall family inet filter FBF-filter term 1 then routing-instance FBF-instance RIB Group:
A RIB (Routing Information Base) group is necessary to share routes between the primary routing table and the custom routing instance. This allows FBF traffic to use the routing information from other routing tables.
Command Example:
set routing-options rib-groups FBF-group import-rib inet.0
set routing-instances FBF-instance routing-options rib-group FBF-group
Juniper
Reference: FBF Configuration: Filter-based forwarding requires these specific steps to redirect traffic to a custom routing table based on filter criteria.
Question #29
Which of the following is a key benefit of implementing High Availability (HA) in a network?
- A . Reduced network security
- B . Increased network downtime
- C . Enhanced data redundancy
- D . Slower data recovery
Correct Answer: C
Question #30
Exhibit:
R2 received an OSPF update from R1, and it received the same update from R3.
Referring to the exhibit, what will R2 do?
- A . R2 ignores the update from R1.
- B . R2 does nothing with R3’s update.
- C . R2 ignores the update from R3.
- D . R2 acknowledges R3 and discards it.
Correct Answer: C
C
Explanation:
In the exhibit, R2 receives the same OSPF update from both R1 and R3. OSPF has mechanisms to prevent unnecessary processing of duplicate LSAs (Link-State Advertisements).
Step-by-Step Breakdown:
OSPF LSA Processing:
OSPF uses LSAs to exchange link-state information between routers. When a router receives an LSA, it checks if it already has a copy of the LSA in its Link-State Database (LSDB).
Duplicate LSAs:
If R2 has already received and processed the update from R1, it will ignore the update from R3 because it already has the same LSA in its database. OSPF uses the concept of flooding, but it does not reprocess LSAs that it already knows about.
R2 Behavior:
R2 will keep the update from R1 (the first one it received) and will ignore the same LSA from R3, as it
is already in the LSDB.
Juniper
Reference: OSPF LSA Processing: Junos adheres to OSPF standards, ensuring that duplicate LSAs are not processed multiple times to avoid unnecessary recalculations.
C
Explanation:
In the exhibit, R2 receives the same OSPF update from both R1 and R3. OSPF has mechanisms to prevent unnecessary processing of duplicate LSAs (Link-State Advertisements).
Step-by-Step Breakdown:
OSPF LSA Processing:
OSPF uses LSAs to exchange link-state information between routers. When a router receives an LSA, it checks if it already has a copy of the LSA in its Link-State Database (LSDB).
Duplicate LSAs:
If R2 has already received and processed the update from R1, it will ignore the update from R3 because it already has the same LSA in its database. OSPF uses the concept of flooding, but it does not reprocess LSAs that it already knows about.
R2 Behavior:
R2 will keep the update from R1 (the first one it received) and will ignore the same LSA from R3, as it
is already in the LSDB.
Juniper
Reference: OSPF LSA Processing: Junos adheres to OSPF standards, ensuring that duplicate LSAs are not processed multiple times to avoid unnecessary recalculations.