View Full Huawei H12-831 Exam Dumps and Practice Test Dumps

 

Question 281.

In OSPF, what is the primary purpose of the Router ID?

1. Uniquely identify the OSPF router within the routing domain
2. Determine interface bandwidth
3. Create an MPLS label
4. Set the VLAN ID

Correct Answer: 1. Uniquely identify the OSPF router within the routing domain

Explanation:

The OSPF Router ID is a 32-bit value used to uniquely identify a router in the OSPF routing domain. It appears in protocol exchanges and LSAs and is also used as a tiebreaker in certain processes, such as DR and BDR elections when interface priorities are equal. Duplicate Router IDs can create routing problems, so each participating router should use a unique value. The Router ID does not directly determine interface bandwidth, VLAN assignment, or MPLS label values.

Question 282.

What is the purpose of OSPF Link State Update packets?

1. Elect the DR only
2. Carry one or more LSAs between OSPF routers
3. Configure interface addresses
4. Advertise BGP communities

Correct Answer: 2. Carry one or more LSAs between OSPF routers

Explanation:

Link State Update packets transport LSAs between OSPF neighbors. They are used during database synchronization and whenever topology information changes and must be flooded through the area or domain according to the LSA type. A single Link State Update packet can contain multiple LSAs. Reliable delivery is supported by Link State Acknowledgment packets. These updates allow routers to maintain synchronized link-state databases and perform accurate SPF calculations based on current topology information.

Question 283.

What is the main purpose of an OSPF Type 2 Network LSA?

1. Advertise external routes
2. Represent inter-area prefixes
3. Describe a multi-access network and the routers attached to it
4. Carry BGP attributes

Correct Answer: 3. Describe a multi-access network and the routers attached to it

Explanation:

A Type 2 Network LSA is generated by the Designated Router on an OSPF multi-access network such as Ethernet. It represents the shared network as a pseudonode and identifies the routers connected to the segment. This approach reduces topology complexity compared with modeling every router-to-router relationship separately. Type 1 LSAs describe individual routers, Type 3 LSAs carry inter-area reachability, and Type 5 LSAs advertise external routes.

Question 284.

Which OSPF path type represents a destination learned from another OSPF area?

1. Intra-area
2. External Type 2 only
3. Connected
4. Inter-area**

Correct Answer: 4. Inter-area

Explanation:

An inter-area OSPF route reaches a destination located in a different OSPF area. Area Border Routers advertise this reachability between areas, commonly through Type 3 Summary LSAs. Intra-area routes are destinations learned entirely within the local area. External routes originate outside the OSPF domain and are introduced by an ASBR. OSPF’s distinction between intra-area, inter-area, and external routes supports its hierarchical routing architecture.

Question 285.

Which BGP attribute identifies the next router that should be used to reach an advertised destination?

1. Next_Hop
2. Community
3. Origin
4. Cluster_List

Correct Answer: 1. Next_Hop

Explanation:

The BGP Next_Hop attribute identifies the IP address used as the forwarding next hop for a route. For a BGP path to become usable, the router generally needs to resolve the Next_Hop through its local routing table. This is especially important in iBGP environments where an externally learned next hop may need to be reachable through an IGP or adjusted through configuration. Communities and Origin carry different forms of routing information and do not serve as the forwarding next-hop address.

Question 286.

What is the main purpose of the BGP Hold timer?

1. Determine route preference
2. Define how long a BGP router waits without receiving expected messages before declaring the peer unavailable
3. Select the best MED
4. Configure route reflection

Correct Answer: 2. Define how long a BGP router waits without receiving expected messages before declaring the peer unavailable

Explanation:

The BGP Hold timer limits how long a router can go without receiving an appropriate BGP message from its peer before considering the session down. Keepalive messages are normally exchanged often enough to prevent the Hold timer from expiring during healthy operation. If the peer becomes unreachable and no messages arrive, expiration causes the BGP session to be terminated and affected routes to be withdrawn. BFD can be used when faster failure detection is required.

Question 287.

Which BGP message type is used to advertise new routes or withdraw previously advertised routes?

1. OPEN
2. KEEPALIVE
3. UPDATE
4. NOTIFICATION only

Correct Answer: 3. UPDATE

Explanation:

BGP UPDATE messages carry routing information between established BGP peers. They can advertise reachable prefixes together with path attributes or withdraw destinations that are no longer reachable. OPEN messages are used when establishing a session, KEEPALIVE messages help maintain it, and NOTIFICATION messages report errors and close the session. UPDATE processing is therefore central to how BGP exchanges and changes routing information.

Question 288.

What is the purpose of a BGP KEEPALIVE message?

1. Carry full routing tables
2. Advertise MPLS labels
3. Assign the router ID
4. Maintain an established BGP session and prevent the Hold timer from expiring**

Correct Answer: 4. Maintain an established BGP session and prevent the Hold timer from expiring

Explanation:

BGP KEEPALIVE messages contain no route advertisements. Their purpose is to indicate that the peer remains operational and to prevent the negotiated Hold timer from expiring when there are no UPDATE messages to send. If neither KEEPALIVE nor other acceptable BGP messages arrive within the Hold time, the peer relationship can be declared down. This mechanism provides normal BGP session liveness, while technologies such as BFD can provide faster failure detection where necessary.

Question 289.

In IS-IS, what is the main role of the SPF algorithm?

1. Calculate shortest paths using the link-state database
2. Elect the DIS only
3. Assign MPLS labels
4. Configure route reflectors

Correct Answer: 1. Calculate shortest paths using the link-state database

Explanation:

IS-IS is a link-state routing protocol. Routers first build a topology database from received LSPs and then run the Shortest Path First algorithm to calculate the best routes through that topology. Changes in link state can trigger database updates and new SPF calculations. The resulting paths can then be installed in the routing table according to route-selection rules. SPF does not assign MPLS labels or configure BGP route-reflector functions.

Question 290.

What is the primary purpose of IS-IS wide metrics?

1. Disable metric-based routing
2. Support a larger metric range and more flexible modern IS-IS extensions
3. Replace the system ID
4. Configure VRRP priorities

Correct Answer: 2. Support a larger metric range and more flexible modern IS-IS extensions

Explanation:

Wide metrics expand the metric capabilities available in IS-IS compared with older narrow metric formats. This provides a larger usable metric range and supports modern extended reachability information carried through TLVs. Wide metrics are useful in larger and more complex networks where greater metric flexibility is required. They do not replace the IS-IS system ID or change first-hop redundancy settings such as VRRP priority.

Question 291.

What does MPLS label swapping accomplish on a transit router?

1. Remove all customer IP information
2. Create a BGP route reflector
3. Replace an incoming label with the appropriate outgoing label
4. Assign an address to the packet source

Correct Answer: 3. Replace an incoming label with the appropriate outgoing label

Explanation:

A transit Label Switching Router examines the top MPLS label, finds the matching forwarding entry, replaces that incoming label with an outgoing label, and forwards the packet toward the next hop. This operation is known as label swapping and is fundamental to MPLS forwarding through the core. The router does not need to alter customer source addressing or act as a BGP route reflector as part of the label-swap operation.

Question 292.

What is the purpose of penultimate hop popping in MPLS?

1. Add a second VPN label
2. Convert MPLS to Ethernet bridging
3. Increase LDP neighbor count
4. Remove the outer transport label before the packet reaches the egress LSR**

Correct Answer: 4. Remove the outer transport label before the packet reaches the egress LSR

Explanation:

Penultimate hop popping allows the router immediately before the egress LSR to remove the outer transport label. This reduces label-processing work on the egress router. If the packet belongs to an MPLS VPN, an inner service label may remain so the egress PE can identify the proper VPN context. PHP is therefore an optimization within MPLS forwarding and does not eliminate the possibility of additional labels remaining in the stack.

Question 293.

In MPLS Layer 3 VPNs, what is the main purpose of MP-BGP between PE routers?

1. Exchange VPN routing information across the provider network
2. Configure customer VLANs
3. Elect the OSPF DR
4. Provide physical link aggregation

Correct Answer: 1. Exchange VPN routing information across the provider network

Explanation:

MP-BGP allows PE routers to exchange VPN routing information using VPN-specific address families. Route Distinguishers make overlapping customer prefixes unique, while Route Targets control which VPN instances import or export those routes. MPLS provides the forwarding mechanism across the provider core. Together, MP-BGP and MPLS allow geographically separated customer sites to participate in the same Layer 3 VPN without exposing all customer routes to core P routers.

Question 294.

What is the primary role of a CE router in an MPLS Layer 3 VPN?

1. Switch MPLS labels through the provider core
2. Connect the customer network to a provider PE router
3. Maintain all provider VPN routes
4. Act as the provider route reflector

Correct Answer: 2. Connect the customer network to a provider PE router

Explanation:

The Customer Edge router belongs to the customer network and connects to the provider’s PE router. It exchanges customer routes with the PE using a supported routing method, which may include static routing or a dynamic protocol. The CE normally does not participate in the provider’s MPLS core or maintain the provider’s VPN control-plane information. MPLS processing and VPN route distribution are handled by the provider infrastructure.

Question 295.

Which VRRP device normally forwards traffic sent to the virtual gateway address?

1. The current master router
2. Every backup simultaneously
3. The OSPF DR
4. The BGP route reflector

Correct Answer: 1. The current master router

Explanation:

The VRRP master is responsible for forwarding traffic associated with the virtual gateway used by hosts. Backup routers monitor the master’s advertisements and stand ready to take over if the master becomes unavailable. This allows hosts to continue using the same default gateway IP address during failover. Tracking and preemption can influence which router becomes master, but only the active master normally performs the virtual gateway forwarding role at a given time.

Question 296.

What is a major benefit of combining VRRP with upstream route tracking?

1. It replaces dynamic routing
2. It can move gateway mastership away from a router that has lost important upstream reachability
3. It automatically creates MPLS labels
4. It changes the Ethernet MTU

Correct Answer: 2. It can move gateway mastership away from a router that has lost important upstream reachability

Explanation:

Without tracking, a router may remain VRRP master because its LAN-facing interface is healthy even though its upstream route has failed. Tracking allows the router’s effective VRRP priority to decrease when an important route or interface becomes unavailable. A backup router with working upstream connectivity can then assume the master role. This makes first-hop redundancy more effective because the active gateway is selected based on broader path health rather than only local link status.

Question 297.

What is the purpose of a standby member in an LACP Eth-Trunk design?

1. Provide a replacement link if an active member becomes unavailable
2. Advertise BGP prefixes
3. Configure OSPF summarization
4. Assign MPLS Route Targets

Correct Answer: 1. Provide a replacement link if an active member becomes unavailable

Explanation:

When an aggregation has more candidate member links than the number allowed to forward actively, some links may remain in standby. If an active member fails, an eligible standby link can become active and restore the desired member count. LACP priorities can influence which interfaces are active or standby. This provides additional resilience while allowing administrators to control the composition of the logical Eth-Trunk.

Question 298.

Which QoS mechanism attempts to avoid severe congestion by dropping selected packets before a queue becomes completely full?

1. Traffic shaping
2. Congestion avoidance such as WRED
3. VRRP tracking
4. Route reflection

Correct Answer: 2. Congestion avoidance such as WRED

Explanation:

Congestion avoidance mechanisms can begin dropping selected packets before a queue is completely full. WRED is an example that can apply different drop behavior according to traffic markings or configured thresholds. Early packet drops can encourage responsive transport protocols to reduce their sending rates before severe congestion occurs. This differs from queue scheduling, which determines transmission order, and shaping, which buffers traffic to control output rate.

Question 299.

Why is BFD useful in a network with redundant routed paths?

1. It can identify a failed forwarding path quickly so routing protocols can converge to an alternative
2. It provides route summarization
3. It replaces BGP attributes
4. It assigns VLAN IDs

Correct Answer: 1. It can identify a failed forwarding path quickly so routing protocols can converge to an alternative

Explanation:

BFD performs rapid liveness detection between network endpoints. When a path fails, BFD can notify the associated routing protocol much sooner than ordinary protocol timers in many designs. OSPF, IS-IS, or BGP can then withdraw affected routes or select an alternate path. BFD itself does not calculate routes, but it can significantly reduce the time required to recognize a forwarding failure and begin convergence.

Question 300.

Which design practice BEST reduces the risk of routing instability in a large Huawei network?

1. Redistribute all routes between every routing protocol
2. Use only one Layer 2 broadcast domain
3. Disable route filtering
4. Use controlled redistribution, route filtering, summarization, redundancy, fast failure detection, and clear protocol boundaries**

Correct Answer: 4. Use controlled redistribution, route filtering, summarization, redundancy, fast failure detection, and clear protocol boundaries

Explanation:

Routing stability depends on limiting unnecessary complexity and controlling how information moves between protocols. Route filtering and controlled redistribution help prevent routing loops and accidental route leaks. Summarization reduces routing-table size and limits the scope of topology changes. Redundant paths and BFD improve availability when failures occur. Clear protocol boundaries make troubleshooting easier and prevent OSPF, IS-IS, BGP, MPLS, VRRP, and related technologies from interacting in unexpected ways.