[Oct-2025] The Best Nokia Network Routing Specialist II Study Guide for the 4A0-112 Exam
4A0-112 certification guide Q&A from Training Expert Actual4Labs
Nokia 4A0-112 certification exam is a valuable certification for network professionals who want to advance their careers in the networking industry. Nokia IS-IS Routing Protocol certification demonstrates that the candidate has a deep understanding of the IS-IS protocol and its applications, which is a critical skill in service provider environments. Holding this certification can lead to new job opportunities and higher salaries.
NEW QUESTION # 24
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 updates its database with the new sequence number and floods a copy of the LSP to its other neighbors.
- B. The router sends a PSNP to its neighbor to request a copy of the LSP.
- C. The router sends a copy of the referenced LSP from its database to its neighbor.
- D. The router sends a CSNP to its neighbor describing the newer LSPs in its database.
Answer: C
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 # 25
Two IS-IS routers are exchanging Hello packets. One is configured to use authentication and the other is not. Which of the following statements is TRUE?
- A. An adjacency will be established without authentication.
- B. An adjacency will be established with authentication using the default parameters defined for IS-IS routers.
- C. The two routers will negotiate the authentication parameters and the establish an adjacency.
- D. An adjacency will not be established.
Answer: D
Explanation:
IS-IS routers must have matching authentication settings to establish an adjacency. If one router is configured with authentication and the other is not, the routers will not be able to establish an adjacency because their authentication parameters do not match.
NEW QUESTION # 26
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 # 27
Refer to the exhibit.
In the IS-IS network shown, router R1 has been configured to summarize subnetworks 20.20.1.0/24 and 20.20.2.0/24 as 20.20.0.0/16. Which routers' routing tables will be reduced, compared to their routing tables before the summarization?
- A. Router R2
- B. Router R1
- C. Routers R2 and R4
- D. Routers R1 and R2
Answer: A
Explanation:
Router R1 is the one that performs the summarization of the two subnets (20.20.1.0/24 and 20.20.2.0/24) into the summarized route 20.20.0.0/16. However, R1 itself will not see any change in its routing table because it is directly connected to both subnets and already knows about them.
Router R2, which is in Area 49.0002, will benefit from this summarization because it previously had separate routes for both 20.20.1.0/24 and 20.20.2.0/24. After the summarization, R2 will only need to maintain a single route to 20.20.0.0/16, reducing the size of its routing table.
Router R4 does not directly benefit from the summarization because it is only connected to the Level 1 network and has no need for the summarized routes from R1. Thus, the summarization does not affect R4's routing table.
NEW QUESTION # 28
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. The neighbors are identified using their interface MAC addresses on broadcast Hello messages and using their system IDs on point-to-point Hello messages.
- 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. Broadcast Hello messages identify the elected designed IS (DIS) and point-to-point Hello messages do not.
Answer: B
Explanation:
In both broadcast and point-to-point interfaces, IS-IS routers identify neighbors using system IDs, not interface MAC addresses. The system ID is a unique identifier assigned to each router, and it is used to identify neighbors in both types of interfaces.
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-R5-R3-R1).
- B. Router R1 to router R7 will follow (R1-R2-R4-R6-R7). Router R7 to router R1 will follow (R7-R6-R4-R2-R1).
- C. Router R1 to router R7 will follow (R1-R2-R4-R6-R7). Router R7 to router R1 will follow (R7-R6-R5-R3-R1).
- D. Router R1 to router R7 will follow (R1-R3-R5-R6-R7). Router R7 to router R1 will follow (R7-R6-R4-R2-R1).
Answer: B
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
A series of actions are triggered on a router as a result of enabling both loopfree-alternate for a link-state routing protocol and ip-fast-reroute. Which of the following is NOT one of those actions?
- A. Calculating a backup next hop for each known IP prefix, if it exists, that would not create a routing loop if used without informing other routers.
- B. Calculating the shortest-path next hop for each known IP prefix.
- C. Enabling the router to locally repair the active path to an IP prefix in case of failure.
- D. Installing two entries in the FIB for IP prefixes, one active and one in standby mode.
Answer: B
NEW QUESTION # 31
When a router performs the SPF calculation, which router is used as the root of the shortest path tree?
- A. The router doing the calculation.
- B. The router with the lowest router ID.
- C. The router's closest neighbor.
- D. The router with the fewest links.
Answer: A
Explanation:
When a router performs the SPF (Shortest Path First) calculation, it uses itself as the root of the shortest path tree (SPT). This router computes the shortest paths to all other routers in the network, treating itself as the origin and calculating the paths based on its view of the network.
NEW QUESTION # 32
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 agree on the result of the DIS election.
- B. The routers discard the received Hello messages because they are not the expected type: LAN Hello vs point-to-point Hello.
- C. The routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast MAC addresses.
- D. The routers do not receive each other's Hello messages because they listen for messages transmitted to different multicast IP addresses.
Answer: B
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 # 33
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. Control Processing Module (CMP)
- B. Media Dependent Adapter (MDA)
- 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 # 34
A routing domain uses a link-state routing protocol. Which of the following would NOT be an advantage of dividing the entire routing domain into areas?
- A. Detailed topology information is only shared among routers within the same area, thus reducing the complexity of the SPF calculation.
- B. Route tables can be reduced by summarizing the IP prefixes advertised between areas.
- C. Fewer routers are required to handle the same amount of traffic, as compared to a single-area domain.
- D. Less-capable routers can be isolated from having to keep track of IP prefixes that are external to the local routing domain.
Answer: C
Explanation:
Dividing a domain into areas typically does not reduce the number of routers needed to handle traffic. It is more focused on improving scalability, reducing the size of routing tables, and limiting the scope of SPF calculations, but it doesn't inherently reduce the number of routers required.
NEW QUESTION # 35
Which of the following statements regarding the databases used by a link-state routing protocol in a single-are routing domain is FALSE?
- A. The adjacency database contains information about all the links interconnecting the domain's routers.
- B. The link-state database is the same for all routers.
- C. The link-state database has the local topology and IP reachability information advertised by all the routers.
- D. The forwarding database contains the optimum next hop for each known prefix.
Answer: A
Explanation:
The adjacency database contains information about the state of the router's adjacencies (i.e., the routers that it is directly connected to and has established a neighbor relationship with). It does not store information about all links in the domain; that information is stored in the link-state database.
NEW QUESTION # 36
Refer to the exhibit.
Which of the following statements best describes the IS-IS domain to which the command output corresponds?
- A. Single-area IS-IS domain with no broadcast interfaces.
- B. Multi-area IS-IS domain with broadcast interfaces.
- C. Single-area IS-IS domain with broadcast interfaces.
- D. Multi-area IS-IS domain with no broadcast interfaces.
Answer: B
Explanation:
The output shows two levels of IS-IS databases: Level 1 (L1) and Level 2 (L2). This indicates that the domain is multi-area, as L1 routers are confined to a single area, while L2 routers can route between different areas. The presence of Level 1/Level 2 (L1/L2) routers also suggests that the domain spans multiple areas.
The LSP (Link-State PDU) entries show L1/L2 ATT attributes, which typically indicate that these routers are capable of routing both within their own area (Level 1) and across areas (Level 2), suggesting a multi-area design.
The IS-IS domain likely includes broadcast interfaces, as indicated by the "ATT" attribute (typically referring to the type of interface) and common IS-IS configuration practices on broadcast networks like Ethernet.
NEW QUESTION # 37
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-R2-R5-R6).
- B. Router R6 to router R3 will follow (R6-R5-R7-R4-R3). Router R3 to router R6 will follow (R3-R4-R7-R5-R6).
- C. Router R6 to router R3 will follow (R6-R5-R2-R3). Router R3 to router R6 will follow (R3-R4-R2-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: A
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 # 38
Refer to the exhibit.
Routers R1 through R4 are running an IGP in such a way that they have each other's system IP addresses in their routing tables. A static route is configured on router R1 so that it can reach subnetwork 10.4.100.0/24. The network administrator decides to use an indirect static route, as shown in the diagram. However, pinging the server from router R1 fails. What may be the problem in this case?
- A. Router R2 drops the echo request because it does not have subnet 10.4.100.0/24 in its routing table.
- B. Router R1 drops the echo request because address 10.10.10.3 does not belong to an adjacent router.
- C. Router R3 drops the echo request because it does not have subnet 10.4.100.0/24 in its routing table.
- D. The echo request arrives at the server but there is no path for the echo response to return to router R1.
Answer: D
Explanation:
The static route configured on router R1 uses an indirect next-hop, which is 10.10.10.3 (R3). While the echo request from R1 reaches the server through the IGP, the problem lies in the return path for the echo response.
The route 10.4.100.0/24 is reachable through R3, but there is no reciprocal route in R3's routing table that allows the response to flow back towards R1. This results in a failure to return the echo response to R1, causing the ping to fail.
NEW QUESTION # 39
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 system ID.
- B. The router with the highest interface MAC address.
- C. The Hello packet with the highest sequence number.
- D. The existing DIS remains the DIS.
Answer: A
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 # 40
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 time taken by the switches to detect that the physical ports are down.
- B. The value of the Ethernet hello timers on the switches.
- C. The value of the BFD transmit interval, receive interval and multiplier settings on routers R1 and R3.
- D. The value of the routing protocol hello timers on routers R1 and R3.
Answer: C
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 # 41
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