Ultimate Guide to Prepare Free Nokia 4A0-112 Exam Questions and Answer
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NEW QUESTION # 15
A router running a link-state routing protocol detects that one of its neighbors is no longer connected to it. The router generates a new link-state advertisement to inform other routers of the topology change. Which of the following is NOT an action that is triggered by this event?
- A. If a router receives multiple copies of the new link-state advertisement, it will simply ignore all copies received after the first one.
- B. Every router that receives the new link-state advertisement updates its age field before forwarding it.
- C. If a router receives the new link-state advertisement, it acknowledges it, stores it, and forwards it to its own neighbors.
- D. Every router that receives the new link-state advertisement runs the SPF algorithm to recalculate its shortest-path tree and its forwarding database.
Answer: B
Explanation:
When a router receives a link-state advertisement (LSA), it does not update the age field before forwarding it. The age field in an LSA is typically updated by the originating router or during the process of forwarding the LSA within the network. Routers do not modify the age field upon receiving and forwarding an LSA.
NEW QUESTION # 16
When multiple routing protocols offer a route for the same prefix, what part of the router is in charge of deciding which route to make active?
- A. The equal cost multipath configuration
- B. The routing information base (RIB)
- C. The forwarding information base (FIB)
- D. The routing table manager (RTM)
Answer: D
Explanation:
The routing table manager (RTM) is responsible for selecting the best route when multiple routing protocols provide a route for the same destination prefix. It makes the decision on which route to add to the routing table based on the administrative distance, metric, and other criteria.
NEW QUESTION # 17
A new router is added to a broadcast network. What does IS-IS use as the tiebreaker for selecting the DIS if the priorities are the same?
- A. The router with the highest interface MAC address.
- B. The Hello packet with the highest sequence number.
- C. The existing DIS remains the DIS.
- D. The router with the highest system ID.
Answer: D
Explanation:
In IS-IS, the Designated Intermediate System (DIS) is responsible for certain tasks on broadcast networks, such as generating link-state advertisements and acting as the central point for flooding information.
NEW QUESTION # 18
Two IS-IS neighboring routers are trying to establish an adjacency, but the interface has been configured as broadcast on one of them and as point-to-point on the other. Why is the adjacency not established?
- A. The routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast MAC addresses.
- B. The routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast IP addresses.
- C. The routers do not agree on the result of the DIS election.
- D. The routers discard the received Hello messages because they are not the expected type: LAN Hello vs point-to-point Hello.
Answer: D
Explanation:
IS-IS routers use different types of Hello messages depending on whether the interface is configured as a broadcast (LAN) or point-to-point (P2P) link.
On a broadcast network (e.g., Ethernet), IS-IS routers use LAN Hello packets to establish adjacencies.
On a point-to-point link, IS-IS uses point-to-point Hello packets.
If one router is configured for a broadcast interface and the other for point-to-point, they will exchange incompatible Hello packets, and as a result, neither router will accept the other's Hello messages, preventing the adjacency from being established.
NEW QUESTION # 19
Which of the following is NOT a function of the control plane a router?
- A. To utilize the forwarding tables to forward data packets towards their destination.
- B. To determine the best way to forward packets.
- C. To establish routing paths to deliver packets from source to destination and to reestablish them in case of failure.
- D. To exchange signaling messages with other routers.
Answer: A
Explanation:
The data plane (or forwarding plane) is responsible for actually forwarding the data packets. It uses the information stored in the forwarding table to determine how to move packets from one interface to another toward their destination.
NEW QUESTION # 20
There are several differences between IS-IS Hello packets used on broadcast interfaces and on point-to-point interfaces.
Which of the following statements is FALSE?
- A. The multicast MAC addresses to which the Hello messages are sent are different on broadcast interfaces and on point-to-point interfaces.
- B. Broadcast Hello messages identify the elected designed IS (DIS) and point-to-point Hello messages do not.
- C. On broadcast interfaces there are different Hello packet types for level-1 and level-2 adjacencies, whereas on point-to-point interfaces there is a single Hello packet type.
- D. The neighbors are identified using their interface MAC addresses on broadcast Hello messages and using their system IDs on point-to-point Hello messages.
Answer: D
NEW QUESTION # 21
When using IS-IS in native mode for routing in a dual-stack IPv4/IPv6 environment, which of the following statements is FALSE?
- A. All links are assumed to be IPv4- and IPv6-capable.
- B. It may lead to traffic black-holing if not properly designed.
- C. In a multi-area environment, the SPF algorithm needs to be run four times on each L1/L2 router.
- D. The same topology information is used to calculate the shortest path tree for both IPv4 and IPv6.
Answer: C
Explanation:
In a dual-stack IPv4/IPv6 IS-IS environment, the SPF (Shortest Path First) algorithm is only run once per router for each protocol (IPv4 or IPv6). The topology is shared, but the SPF calculations for IPv4 and IPv6 are separate. This means that the SPF algorithm will run twice (once for IPv4 and once for IPv6) for each L1/L2 router, not four times.
NEW QUESTION # 22
Which of the following definitions best describes route redistribution?
- A. It is the process of passing routing information from one routing domain to another, which usually means from one routing protocol to another.
- B. It is the process of deciding at line-rate speed which packets will be dropped and which ones will be forwarded.
- C. It is the process of redirecting packets to be processed by an intermediate network function before allowing them to be forwarded to their intended final destination.
- D. It is the process of controlling which route advertisements received from routing peers are accepted and/or deciding which locally known prefixes are advertised to routing peers.
Answer: A
Explanation:
Route redistribution is the process of sharing routing information between different routing protocols or routing domains. For example, a router might redistribute routes learned via OSPF into a BGP routing table or vice versa. This enables routers to exchange routing information even when they are using different routing protocols.
NEW QUESTION # 23
Refer to the exhibit.
Static routing is to be used in a network between a corporate head office and a branch office. The head office has many connected subnetworks, whereas the branch office has one subnetwork and a single connection to the head office. Which of the following is the most likely configuration on the head office and branch office routers?
- A. The head office has a specific static route and the branch office has a default route.
- B. The head office has a default route and the branch office has a specific static route.
- C. The head office and the branch office both have default routes.
- D. The head office and the branch offices both have specific static routes.
Answer: B
Explanation:
The head office has many connected subnetworks, so it will typically have a default route to forward traffic to the branch office (or external networks), since it may not need to define static routes for each branch network.
The branch office, which has only one subnetwork and a single connection to the head office, will have a specific static route to reach the head office subnet or other subnets at the head office, since it only needs to know the specific route to reach the head office's network.
NEW QUESTION # 24
Refer to the exhibit.
All routers in the diagram are running an interior gateway protocol (IGP) and have been configured with an ECMP value of 4. Router R5 advertises the prefix 192.168.3.0/24 using the IGP. Assuming all links have the same cost, how many entries for prefix 192.168.3.0/24 will be in router R3's routing table?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: A
Explanation:
In this scenario, the routers are configured with an Equal-Cost Multi-Path (ECMP) value of 4, meaning they can utilize up to 4 equal-cost paths to reach a destination. Since Router R5 is advertising the 192.168.3.0/24 prefix and all links have the same cost, router R3 will receive multiple routes to reach this destination.
Given that all the routers (R1, R2, R3, R4, and R5) are connected in a way that can support multiple equal-cost paths, and assuming ECMP is set to 4, the routing table on Router R3 will have up to 4 entries for the prefix 192.168.3.0/24.
Thus, Router R3's routing table will contain 4 entries for the prefix 192.168.3.0/24.
NEW QUESTION # 25
Which of the following statements about the IP forwarding process on a router is TRUE?
- A. It uses the ARP table to find a match for the source MAC address.
- B. It uses the ARP table to find a match for the destination MAC address.
- C. It uses the routing table to find a match for the source IP address.
- D. It uses the routing table to find a match for the destination IP address.
Answer: D
Explanation:
During the IP forwarding process, routers use the routing table to determine the next hop based on the destination IP address. The source IP address is not directly involved in the lookup process for forwarding.
The ARP table is used to map IP addresses to MAC addresses, specifically for resolving the MAC address of the next hop (destination MAC address) for forwarding packets within the local network.
NEW QUESTION # 26
An IS-IS router receives a CSNP that references an older LSP than the one in its local database. What action is taken?
- A. The router sends a copy of the referenced LSP from its database to its neighbor.
- B. The router sends a PSNP to its neighbor to request a copy of the LSP.
- C. The router sends a CSNP to its neighbor describing the newer LSPs in its database.
- D. The router updates its database with the new sequence number and floods a copy of the LSP to its other neighbors.
Answer: A
Explanation:
When a router receives a CSNP (Complete Sequence Number PDU) that references an older LSP (Link-State PDU) than the one in its local database, it indicates that the neighbor is missing newer information.
In response, the router sends back a PSNP (Partial Sequence Number PDU) to the neighbor, which includes a copy of the LSPs it has in its local database that the neighbor may not yet have. This helps to synchronize the link-state information between routers.
NEW QUESTION # 27
Refer to the exhibit.
In the diagram, all routers are using IS-IS as their routing protocol. The number next to each link is its metric value.
What path will traffic follow from router R6 to router R3, and from router R3 to router R6?
- A. Router R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R4-R2-R5-R6).
- B. Router R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R2-R5-R6).
- C. Router R6 to router R3 will follow (R6-R5-R7-R4-R3). Router R3 to router R6 will follow (R3-R4-R7-R5-R6).
- D. Router R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R4-R7-R5-R6).
Answer: B
Explanation:
The metric values between the routers dictate the routing paths, and IS-IS will calculate the shortest path based on these values.
R6 to R3: The path from R6 to R3 will go through R5 and R2, as this route has the least cumulative metric (10 + 10 + 15 = 35).
R3 to R6: The reverse path from R3 to R6 will follow R3 → R2 → R5 → R6 because this route is also the shortest with a total metric of 10 + 10 + 10 = 30.
NEW QUESTION # 28
Which component of the Nokia 7750 SR is in charge of performing the longest prefix match lookup on packets that arrive on the physical interfaces?
- A. Media Dependent Adapter (MDA)
- B. Control Processing Module (CMP)
- C. Input/Output Module (IOM)
- D. Switch Fabric (SF)
Answer: C
Explanation:
The Input/Output Module (IOM) is responsible for performing the longest prefix match (LPM) lookup on packets that arrive at the physical interfaces. The IOM performs this function by examining the destination IP address of incoming packets and using the routing table to determine the best match.
NEW QUESTION # 29
Refer to the exhibit.
In the diagram, all routers are using IS-IS as their routing protocol. The number next to each link is its metric value.
What path will traffic follow from router R1 to router R7, and from router R7 to router R1?
- A. Router R1 to router R7 will follow (R1-R3-R5-R6-R7). Router R7 to router R1 will follow (R7-R6-R4-R2-R1).
- B. Router R1 to router R7 will follow (R1-R3-R5-R6-R7). Router R7 to router R1 will follow (R7-R6-R5-R3-R1).
- C. Router R1 to router R7 will follow (R1-R2-R4-R6-R7). Router R7 to router R1 will follow (R7-R6-R4-R2-R1).
- D. Router R1 to router R7 will follow (R1-R2-R4-R6-R7). Router R7 to router R1 will follow (R7-R6-R5-R3-R1).
Answer: C
Explanation:
From R1 to R7: The path will be R1 → R2 → R4 → R6 → R7 because this path has the least cumulative metric of 10 + 10 + 10 + 10 = 40.
From R7 to R1: The reverse path will follow R7 → R6 → R4 → R2 → R1 because it is the shortest return path with the same metrics.
NEW QUESTION # 30
Which of the following statements about router interfaces on a Nokia 7750 SR is FALSE?
- A. They can be used in pairs on the same subnet for redundancy.
- B. The system interface exists by default.
- C. They can be assigned IPv4 and/or IPv6 addresses.
- D. They can be logical or physical.
Answer: A
Explanation:
Typically, interfaces on a Nokia 7750 SR router are not configured in pairs on the same subnet for redundancy. Instead, redundancy is achieved through mechanisms like Virtual Router Redundancy Protocol (VRRP) or other high availability protocols, not by simply using interfaces in pairs on the same subnet.
NEW QUESTION # 31
Refer to the exhibit.
All routers in the diagram are running a link-state routing protocol. Before the link failure, all routers have operational adjacencies with each other and there is a BFD session between routers R1 and R3. After the link failure, which of the following affects the routing protocol's convergence time?
- A. The value of the Ethernet hello timers on the switches.
- B. The time taken by the switches to detect that the physical ports are down.
- C. The value of the routing protocol hello timers on routers R1 and R3.
- D. The value of the BFD transmit interval, receive interval and multiplier settings on routers R1 and R3.
Answer: D
Explanation:
BFD (Bidirectional Forwarding Detection) is used to detect link failures quickly and helps improve convergence time in link-state routing protocols. The BFD session between routers R1 and R3 allows them to detect the failure of the link between them more quickly than the regular routing protocol hello timers. The transmit interval, receive interval, and multiplier settings determine how fast BFD detects a failure and triggers the routing protocol to converge, which directly impacts the convergence time.
NEW QUESTION # 32
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