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

 

Question 221.

In OSPF, which mechanism determines the preferred path when multiple routes exist to the same destination within the protocol?

1. The path with the lowest accumulated OSPF cost
2. The path with the highest MED
3. The path with the largest VLAN ID
4. The path with the longest AS_Path

Correct Answer: 1. The path with the lowest accumulated OSPF cost

Explanation:

OSPF uses cost as its routing metric and normally selects the route with the lowest total cost to the destination. The total path cost is calculated by adding the outgoing interface costs along the route. Administrators can influence OSPF routing by adjusting interface costs where necessary. MED and AS_Path are BGP attributes and do not determine OSPF path selection. VLAN IDs are Layer 2 identifiers and are unrelated to OSPF metric calculations.

Question 222.

What is the purpose of configuring OSPF authentication between neighboring routers?

1. Increase interface bandwidth
2. Reduce the risk of unauthorized routers participating in OSPF exchanges
3. Create MPLS labels
4. Automatically summarize routes

Correct Answer: 2. Reduce the risk of unauthorized routers participating in OSPF exchanges

Explanation:

OSPF authentication helps ensure that routing protocol packets are accepted only from routers using the expected authentication configuration. This can reduce the risk of unauthorized devices forming adjacencies or injecting incorrect routing information. Neighboring routers must use compatible authentication settings, or adjacency establishment may fail. Authentication does not increase bandwidth or automatically change route summarization behavior. It is a routing-protocol security control that should be combined with secure management and infrastructure filtering.

Question 223.

Which OSPF condition can prevent two routers from forming a full adjacency even though they are directly connected?

1. Identical router IDs
2. Matching Hello timers
3. Incompatible OSPF interface parameters such as area or authentication settings
4. Equal OSPF costs

Correct Answer: 3. Incompatible OSPF interface parameters such as area or authentication settings

Explanation:

Direct IP connectivity is not enough for OSPF adjacency. Neighboring routers must agree on key protocol settings, including area membership, authentication, Hello and Dead timers, and compatible network behavior. If these settings are inconsistent, routers may receive packets from one another but fail to progress to a full neighbor relationship. Administrators should compare interface-level OSPF parameters first when troubleshooting adjacency problems. Equal cost does not prevent an adjacency from forming.

Question 224.

Why is OSPF route summarization generally performed at area boundaries?

1. To disable backbone connectivity
2. To increase LSA flooding
3. To create VRRP groups
4. To reduce routing detail propagated between areas**

Correct Answer: 4. To reduce routing detail propagated between areas

Explanation:

OSPF’s hierarchical area structure allows summarization at area boundaries, usually on ABRs. Multiple related prefixes can be represented by a broader summary route when the address plan supports aggregation. This reduces routing-table size and limits the impact of detailed topology changes on routers in other areas. Summarization should be planned carefully because poorly chosen aggregates can attract traffic toward unavailable destinations. It is a scalability mechanism rather than a replacement for the OSPF backbone.

Question 225.

Which BGP attribute is normally preferred when its value is higher and is distributed within the local autonomous system?

1. Local Preference
2. MED
3. AS_Path length
4. Origin code

Correct Answer: 1. Local Preference

Explanation:

Local Preference is commonly used to influence outbound traffic within an autonomous system. Higher Local Preference values are generally preferred, making the attribute useful when an organization wants one external path to be primary and another to be secondary. The value is shared among iBGP peers but is not normally advertised to external BGP neighbors. MED generally prefers lower values, while AS_Path is evaluated according to path length and other BGP selection rules.

Question 226.

A network administrator wants to influence how an external AS enters the local network across two links. Which BGP attribute can be advertised for this purpose?

1. Router ID
2. MED
3. OSPF cost
4. VRRP priority

Correct Answer: 2. MED

Explanation:

The Multi-Exit Discriminator is designed to suggest which entry point a neighboring autonomous system should prefer when multiple connections exist. Lower MED values are generally preferred when the attribute is compared. MED is advisory, so the neighboring AS can override the suggestion using its own routing policies. It is therefore a useful traffic-engineering tool but not an absolute control over remote routing decisions.

Question 227.

What is the main purpose of BGP prefix filtering at an external network boundary?

1. Increase MPLS forwarding speed
2. Create an Eth-Trunk
3. Limit accepted and advertised routes to approved prefixes
4. Replace AS_Path loop prevention

Correct Answer: 3. Limit accepted and advertised routes to approved prefixes

Explanation:

Prefix filtering is a fundamental routing-policy control on eBGP connections. It helps prevent accidental route leaks, unauthorized advertisements, and acceptance of unexpected routes from external peers. Administrators can use prefix lists and route policies to define exactly which networks should be exchanged. Filtering complements BGP’s built-in loop-prevention mechanisms and should be maintained as addressing and business relationships change. It does not replace the AS_Path attribute.

Question 228.

What is the primary benefit of using a BGP route reflector in a large autonomous system?

1. Eliminate the need for any IGP
2. Replace all eBGP sessions
3. Create VPN labels automatically
4. Reduce the number of required iBGP sessions**

Correct Answer: 4. Reduce the number of required iBGP sessions

Explanation:

A traditional iBGP design requires a full mesh of BGP sessions among internal BGP speakers. As the network grows, this becomes difficult to scale. A route reflector can advertise selected iBGP routes between its clients, reducing the number of sessions required. Redundant route reflectors are commonly used to improve control-plane availability. Route reflection does not eliminate the need for an IGP, because underlying IP reachability between BGP speakers still must be maintained.

Question 229.

What is the purpose of the overload bit in IS-IS?

1. Signal that a router should generally not be used as a transit path
2. Increase all interface bandwidths
3. Force the router to become DIS
4. Disable IS-IS adjacency formation

Correct Answer: 1. Signal that a router should generally not be used as a transit path

Explanation:

The IS-IS overload bit can indicate that a router should remain reachable but should not normally be selected as a transit node. This is useful during startup or maintenance when the router’s routing or forwarding state may not yet be fully ready. Other routers can calculate alternate transit paths while still retaining reachability to destinations directly associated with the overloaded router. The feature can improve stability during operational transitions.

Question 230.

What is the main purpose of the IS-IS DIS on a broadcast network?

1. Replace Level-2 routing
2. Represent the shared network and assist with database synchronization
3. Provide DHCP relay
4. Act as the host default gateway

Correct Answer: 2. Represent the shared network and assist with database synchronization

Explanation:

The Designated Intermediate System performs important functions on an IS-IS broadcast segment. It helps represent the shared multi-access network in the link-state topology and supports synchronization of link-state information. Although the DIS has some conceptual similarity to the OSPF DR, the protocols handle elections and failover differently. The DIS does not provide ordinary host gateway services or replace the Level-2 inter-area routing function.

Question 231.

Which protocol commonly distributes MPLS labels for IGP-reachable prefixes in a traditional MPLS network?

1. OSPF only
2. VRRP
3. LDP
4. STP

Correct Answer: 3. LDP

Explanation:

Label Distribution Protocol is commonly used to exchange label mappings for forwarding equivalence classes associated with IGP routes. The IGP provides reachability and next-hop information, while LDP supplies the labels needed for MPLS forwarding. Together, these mechanisms can establish label-switched paths through the provider network. LDP does not replace OSPF or IS-IS; instead, it works alongside them to provide label-based forwarding.

Question 232.

What is the purpose of an inner VPN label in an MPLS Layer 3 VPN packet?

1. Identify the STP instance
2. Select the OSPF area
3. Encrypt the customer packet
4. Identify the appropriate VPN or forwarding context at the egress PE**

Correct Answer: 4. Identify the appropriate VPN or forwarding context at the egress PE

Explanation:

MPLS Layer 3 VPN traffic often carries a label stack. The outer label transports the packet across the provider core toward the correct PE router, while the inner VPN label identifies the customer VPN or forwarding context at the egress PE. After the transport label is removed, the remaining service label helps the PE determine how to process the packet. This separation allows provider core routers to forward traffic without maintaining all customer VPN routes.

Question 233.

What is the primary function of a Route Distinguisher in an MPLS Layer 3 VPN?

1. Make overlapping customer prefixes unique in the provider control plane
2. Determine VRRP priority
3. Create link aggregation
4. Configure traffic policing

Correct Answer: 1. Make overlapping customer prefixes unique in the provider control plane

Explanation:

Different customers may use identical IPv4 address ranges. A Route Distinguisher is combined with a customer prefix so MP-BGP can treat otherwise identical prefixes as distinct VPN routes. The RD provides uniqueness but does not control which VPN imports a route. Route Targets provide that import and export policy function. This distinction is important when troubleshooting MPLS Layer 3 VPN route distribution.

Question 234.

Which feature controls whether an MPLS VPN route is imported into a particular VPN instance?

1. OSPF cost
2. Route Target
3. LACP priority
4. BFD discriminator only

Correct Answer: 2. Route Target

Explanation:

Route Targets are extended BGP communities used to control VPN route distribution. A VPN instance exports routes with selected Route Targets, and other VPN instances import routes when their configured import policies match those values. This enables flexible service designs such as full-mesh VPNs, hub-and-spoke VPNs, and shared-service topologies. Route Distinguishers provide route uniqueness but do not determine route membership.

Question 235.

What is the main purpose of VRRP in a campus network?

1. Provide redundant default-gateway service to hosts
2. Distribute MPLS labels
3. Replace spanning tree
4. Perform BGP route reflection

Correct Answer: 1. Provide redundant default-gateway service to hosts

Explanation:

VRRP allows multiple routers or Layer 3 switches to share a virtual IP address that hosts use as their default gateway. One device acts as master and forwards traffic, while another can take over if the master becomes unavailable. This protects first-hop connectivity without requiring hosts to change gateway configuration. VRRP can be enhanced with priority tracking and preemption to improve failover behavior, but it does not replace dynamic routing or Layer 2 loop prevention.

Question 236.

Why might a VRRP master track an upstream interface?

1. To increase its permanent priority after failure
2. To reduce its effective priority when upstream connectivity is lost
3. To create an MPLS VPN
4. To disable all backups

Correct Answer: 2. To reduce its effective priority when upstream connectivity is lost

Explanation:

A router can remain reachable to hosts on the local LAN even after losing its upstream connection. If it continues acting as VRRP master, hosts may send traffic to a gateway that cannot reach remote destinations. Tracking an upstream interface or route allows the router’s effective priority to decrease when connectivity fails. A healthier backup router can then assume the master role. This improves gateway resilience by considering end-to-end path availability.

Question 237.

What is the purpose of the load-balancing hash in an Eth-Trunk?

1. Select an active member link for individual traffic flows
2. Encrypt packets across member links
3. Assign OSPF costs
4. Configure BGP communities

Correct Answer: 1. Select an active member link for individual traffic flows

Explanation:

An Eth-Trunk typically distributes traffic using a hashing algorithm based on selected packet fields such as source and destination addresses. This helps spread multiple flows across active member links while preserving packet order within each flow. Because one flow may remain on a single member, the aggregate bandwidth benefit is most visible when multiple flows are present. The hashing function is part of link aggregation and does not change routing-protocol attributes.

Question 238.

Which QoS mechanism should be used when excess traffic should be buffered and transmitted later rather than immediately dropped?

1. Traffic policing
2. Traffic shaping
3. Route redistribution
4. BFD

Correct Answer: 2. Traffic shaping

Explanation:

Traffic shaping regulates the output rate by buffering traffic that temporarily exceeds a configured threshold and transmitting it later. This can smooth bursts and reduce packet loss, although it introduces additional delay. Policing normally takes immediate action on excess traffic by dropping or remarking it instead of buffering it for later transmission. Shaping is therefore appropriate when delayed delivery is preferable to immediate discard and sufficient buffering is available.

Question 239.

Which technology is most appropriate when a routing protocol requires very fast detection of a forwarding-path failure?

1. BFD
2. DHCP relay
3. MSTP only
4. Route Distinguisher

Correct Answer: 1. BFD

Explanation:

Bidirectional Forwarding Detection provides rapid liveness detection independently of normal routing-protocol timers. OSPF, IS-IS, and BGP can use BFD status so they react more quickly to forwarding-path failures. This enables faster convergence without necessarily reducing every native Hello or keepalive timer. BFD itself does not calculate replacement routes; it provides fast failure information to the routing protocol that performs the actual path selection.

Question 240.

Which design approach BEST supports a scalable Huawei network that uses OSPF, IS-IS, BGP, MPLS, VRRP, Eth-Trunk, and QoS?

1. Use unrestricted redistribution and avoid route filtering
2. Keep all services in one large broadcast domain
3. Disable redundancy to reduce configuration
4. Use hierarchical design, clear routing boundaries, summarization, controlled policies, redundancy, fast convergence, and consistent QoS**

Correct Answer: 4. Use hierarchical design, clear routing boundaries, summarization, controlled policies, redundancy, fast convergence, and consistent QoS

Explanation:

Large networks are easier to operate when each protocol has a clearly defined role. Hierarchical topology and structured addressing support route summarization and smaller failure domains. Route policies and filtering control advertisements, while redundancy, VRRP, Eth-Trunk, and BFD improve availability and convergence. MPLS provides scalable service transport, and QoS ensures predictable treatment during congestion. Uncontrolled redistribution and flat Layer 2 design increase complexity and make outages harder to contain and troubleshoot.