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Q181. Which OSPF authentication method provides stronger security by using a cryptographic hash?

1) Plain-text authentication
2) MD5 authentication
3) No authentication
4) Simple password authentication

Correct Answer: 2) MD5 authentication

Explanation:
OSPF authentication can help ensure that routing updates are received only from trusted neighbors. MD5 authentication uses a cryptographic hash to validate OSPF packets and provides stronger protection than plain-text authentication. With MD5, the configured authentication key is not transmitted directly across the network. Both OSPF neighbors must have matching authentication settings and keys for adjacency to form successfully. Plain-text authentication provides significantly weaker protection because the password can potentially be observed by someone monitoring network traffic. Although newer security mechanisms may be preferred in modern deployments, MD5 is a commonly tested OSPF authentication method in CCNP routing scenarios.

Q182. An EIGRP administrator wants a router to perform unequal-cost load balancing across multiple paths. Which feature should be configured?

1) Variance
2) Summarization
3) Stub routing
4) Route poisoning

Correct Answer: 1) Variance

Explanation:
EIGRP supports unequal-cost load balancing using the variance command. By default, EIGRP performs equal-cost load balancing, meaning multiple routes must have the same metric before they can be installed as successors. Variance allows routes with higher metrics to participate in load balancing, provided they satisfy EIGRP’s feasibility requirements. The variance value acts as a multiplier of the best route’s metric. For example, a variance of 2 allows certain feasible paths with metrics up to twice the best metric to be considered. This feature is particularly useful when network paths have different bandwidth or delay characteristics but both can safely forward traffic.

Q183. Which EIGRP feature is designed to prevent a router from becoming a transit router for routes learned from another EIGRP neighbor?

1) Variance
2) Route summarization
3) EIGRP stub
4) Split horizon

Correct Answer: 3) EIGRP stub

Explanation:
EIGRP stub routing is used primarily in branch or spoke routers that should not be used as transit points for routing traffic. When a router is configured as an EIGRP stub, it informs its neighbors that it should not be queried for arbitrary routes. This reduces the scope of EIGRP queries and improves network stability, especially in large or hub-and-spoke environments. An EIGRP stub can be configured to advertise selected types of routes, such as connected, static, summary, or redistributed routes. This makes the feature useful for controlling route propagation while also reducing unnecessary EIGRP query traffic.

Q184. What is the primary purpose of a BGP route reflector?

1) Encrypt BGP updates
2) Eliminate the requirement for full-mesh iBGP
3) Replace OSPF inside an autonomous system
4) Increase the bandwidth of BGP links

Correct Answer: 2) Eliminate the requirement for full-mesh iBGP

Explanation:
A BGP route reflector reduces the need for a full-mesh internal BGP design. Normally, iBGP routers do not advertise routes learned from one iBGP neighbor to another iBGP neighbor, which traditionally requires every iBGP router to establish sessions with every other iBGP router. As the number of routers increases, this becomes difficult to manage. A route reflector provides a scalable alternative by allowing selected clients to exchange routes through the reflector. The route reflector can advertise routes between its clients according to BGP route-reflection rules. This greatly reduces the number of required iBGP sessions in larger networks.

Q185. Which BGP attribute is commonly configured with next-hop-self to ensure that an iBGP peer uses the advertising router as the next hop?

1) MED
2) Local Preference
3) NEXT_HOP
4) AS_PATH

Correct Answer: 3) NEXT_HOP

Explanation:
The BGP NEXT_HOP attribute identifies the IP address that should be used to reach a BGP destination. When a router advertises an external BGP route into an iBGP environment, the original external next-hop address may not be reachable by internal routers. Configuring next-hop-self causes the advertising router to change the BGP next-hop attribute to its own address. This is especially common when an edge router receives routes from an external BGP neighbor and advertises them to internal BGP peers. Without an appropriate next hop, routes may appear in the BGP table but fail to become usable in the routing table.

Q186. Which BGP feature allows an administrator to attach additional information to routes for policy decisions?

1) Communities
2) OSPF areas
3) VLAN tags
4) EIGRP successors

Correct Answer: 1) Communities

Explanation:
BGP communities provide a flexible way to classify routes and apply routing policies. A community is an attribute that can be attached to a BGP route and later matched by route policies or route maps. Network administrators can use communities to identify routes according to business requirements, geographic locations, customers, or routing preferences. Well-known communities such as no-export can also influence how routes are advertised. Communities are especially valuable in service-provider and enterprise environments because they allow routing policy to be communicated without relying exclusively on individual prefixes. This makes large-scale BGP policy management easier and more consistent.

Q187. Which command is commonly used to apply a prefix list to BGP route filtering?

1) ip ospf filter-list
2) neighbor prefix-list
3) router eigrp prefix-list
4) ip route prefix-list

Correct Answer: 2) neighbor prefix-list

Explanation:
The BGP neighbor prefix-list command applies an IPv4 prefix list to routes exchanged with a specific BGP neighbor. Prefix lists provide precise control over which networks are permitted or denied. They can be applied in either the inbound or outbound direction. For example, an administrator might permit only company-owned prefixes to be advertised to an external provider, preventing accidental route leakage. Prefix lists use prefix lengths and network prefixes to make routing decisions. Compared with broad access-list-based filtering, prefix lists are specifically designed for route filtering and provide efficient and readable policy control in BGP configurations.

Q188. Which command can be used to perform a soft reset of BGP policy without tearing down the BGP session?

1) clear ip bgp * soft
2) shutdown bgp
3) reload bgp
4) clear ospf process

Correct Answer: 1) clear ip bgp * soft

Explanation:
A BGP soft reset allows an administrator to reapply routing policies without completely terminating the BGP neighbor relationship. The command clear ip bgp * soft can be used to trigger a soft reset for BGP sessions. This is useful after changing route maps, prefix lists, or other routing policies because it minimizes disruption compared with a hard reset. A hard BGP reset tears down the session and causes routes to be withdrawn and relearned. Soft resets are therefore preferred when possible in production environments because they reduce unnecessary routing instability and service interruption while allowing the updated policy to take effect.

Q189. In an MPLS network, what is primarily used to identify a forwarding equivalence class for packet forwarding?

1) MAC address
2) MPLS label
3) TCP port
4) DNS name

Correct Answer: 2) MPLS label

Explanation:
MPLS forwarding uses labels to identify forwarding equivalence classes and determine how packets should be handled. When an MPLS packet enters the MPLS domain, a label can be assigned to represent a particular forwarding treatment or destination. MPLS routers then examine the label rather than repeatedly performing a traditional IP routing lookup for every hop. Depending on the operation, a router may swap, push, or pop labels. This label-based forwarding mechanism is one of the fundamental concepts behind MPLS. In service-provider networks, MPLS labels support scalable services such as Layer 3 VPNs and Layer 2 VPN technologies.

Q190. Which protocol is commonly used to distribute MPLS labels between routers?

1) FTP
2) LDP
3) DHCP
4) NTP

Correct Answer: 2) LDP

Explanation:
Label Distribution Protocol, or LDP, is commonly used to distribute MPLS labels between routers. LDP establishes relationships between MPLS-enabled routers and allows them to exchange label bindings associated with forwarding information. The routers use these bindings to construct label-switched paths through the MPLS network. LDP commonly works alongside an interior gateway protocol such as OSPF or IS-IS, which provides the underlying IP reachability information. The IGP determines the best paths, while LDP associates labels with those forwarding paths. Understanding the distinction between the IGP and LDP is important when troubleshooting MPLS forwarding and label-switched connectivity.

Q191. Which DMVPN feature allows spokes to dynamically learn a more direct path to another spoke after initially using the hub?

1) NHRP shortcut
2) OSPF DR election
3) BGP MED
4) MPLS PHP

Correct Answer: 1) NHRP shortcut

Explanation:
DMVPN Phase 3 uses NHRP redirect and shortcut mechanisms to improve spoke-to-spoke communication. Initially, traffic may travel through the hub because the spoke does not yet know the direct tunnel information for the destination. The hub can send an NHRP redirect message, informing the spoke that a more direct path is available. The spoke can then use NHRP to resolve the destination spoke’s tunnel information and establish a more efficient forwarding path. This reduces unnecessary traffic through the hub and can improve scalability and performance. NHRP shortcut is therefore an important component of DMVPN Phase 3 operation.

Q192. What is the primary purpose of GRE when it is combined with IPsec?

1) Provide routing protocol encapsulation and IPsec security
2) Replace Ethernet switching
3) Assign DHCP addresses
4) Perform DNS resolution

Correct Answer: 1) Provide routing protocol encapsulation and IPsec security

Explanation:
GRE provides a flexible tunneling mechanism that can encapsulate different types of network traffic, including multicast and routing protocol traffic. However, GRE itself does not provide encryption. IPsec can be combined with GRE to provide confidentiality and integrity for the tunneled traffic. This combination is useful when organizations need to transport routing protocols such as OSPF or EIGRP across an encrypted tunnel. GRE creates the logical tunnel, while IPsec secures the packets. In practice, GRE over IPsec is commonly used for site-to-site connectivity where dynamic routing and encrypted communication are both required.

Q193. Which QoS mechanism is primarily responsible for identifying traffic so that different classes can receive different treatment?

1) Classification
2) Shaping
3) Policing
4) Queuing only

Correct Answer: 1) Classification

Explanation:
QoS classification identifies traffic and places packets into appropriate traffic classes. Classification can be based on characteristics such as source and destination addresses, protocols, applications, DSCP values, or access-control-list matches. Once traffic has been classified, additional QoS actions such as marking, policing, shaping, and queuing can be applied. Classification is therefore an important first step in creating differentiated service policies. For example, voice traffic can be classified separately from bulk data so that it receives appropriate treatment during congestion. Without accurate classification, later QoS mechanisms may not know which packets require priority or special handling.

Q194. Which QoS mechanism can buffer traffic and transmit it at a controlled rate to smooth bursts?

1) Policing
2) Shaping
3) Classification
4) Marking

Correct Answer: 2) Shaping

Explanation:
Traffic shaping controls the rate at which packets leave an interface by buffering excess traffic and transmitting it later according to a configured rate. This makes shaping useful when traffic arrives in bursts but the downstream connection can handle only a certain sustained rate. Because shaping stores excess packets temporarily, it can smooth traffic rather than immediately discarding packets. Policing works differently because it generally measures traffic against a rate and may drop or remark packets that exceed the configured limits. Understanding this distinction is important when designing WAN QoS policies where bursty traffic needs to be controlled without unnecessary packet loss.

Q195. Which mechanism can help prevent TCP traffic from consuming all available queue space during congestion by probabilistically dropping packets before the queue becomes full?

1) WRED
2) LLQ
3) CBWFQ
4) Classification

Correct Answer: 1) WRED

Explanation:
Weighted Random Early Detection, or WRED, helps manage congestion by beginning to drop packets before a queue reaches complete capacity. The mechanism can use packet characteristics such as IP precedence or DSCP to apply different thresholds to different traffic classes. WRED is particularly associated with congestion avoidance and TCP traffic because TCP can respond to packet loss by reducing its transmission rate. By dropping packets probabilistically before a queue becomes completely full, WRED can help avoid a sudden large number of packet drops when the queue overflows. It is therefore different from traditional tail drop, which discards packets only after the queue becomes full.

Q196. Which technology provides flow-level information such as source address, destination address, ports, and byte counts for traffic analysis?

1) NetFlow
2) STP
3) HSRP
4) NTP

Correct Answer: 1) NetFlow

Explanation:
NetFlow provides information about network traffic flows and is useful for monitoring, accounting, troubleshooting, and capacity planning. A flow record can contain information such as source and destination IP addresses, source and destination transport ports, protocol, interface information, packet counts, and byte counts. Administrators can use NetFlow data to determine which applications or hosts are generating significant traffic and to identify unusual traffic patterns. NetFlow does not normally capture the complete contents of packets. Instead, it summarizes flow characteristics, making it much more efficient for traffic analysis. This makes flow monitoring valuable in both enterprise and service-provider environments.

Q197. Which SNMP version provides authentication and encryption capabilities for management traffic?

1) SNMPv1
2) SNMPv2c
3) SNMPv3
4) SNMPv0

Correct Answer: 3) SNMPv3

Explanation:
SNMPv3 provides stronger security features than SNMPv1 and SNMPv2c. It supports authentication to verify the identity of management entities and privacy mechanisms that can encrypt SNMP traffic. SNMPv1 and SNMPv2c commonly use community strings, which do not provide the same level of security as SNMPv3. SNMPv3 can therefore be preferred when network management traffic needs protection against unauthorized access or interception. Its security model includes mechanisms for authentication, integrity, and privacy depending on the configured security level. For modern network-management deployments, understanding SNMPv3 is important because management protocols themselves should also be protected.

Q198. In IPv6, which routing protocol is specifically designed as the IPv6 version of OSPF?

1) OSPFv3
2) RIPv1
3) EIGRPv1
4) BGP-4 only

Correct Answer: 1) OSPFv3

Explanation:
OSPFv3 is designed to support IPv6 routing and is the IPv6 version of the OSPF protocol. It maintains the link-state characteristics of OSPF, including neighbor relationships, link-state databases, and shortest-path calculations. OSPFv3 uses IPv6 link-local addresses for neighbor communication and has several architectural differences from OSPFv2. Understanding OSPFv3 is important for networks transitioning from IPv4 to IPv6 or operating dual-stack environments. Administrators must also understand IPv6-specific concepts such as link-local addressing and IPv6 interface configuration when troubleshooting OSPFv3 adjacencies and route propagation.

Q199. Which route-map capability allows an administrator to select routes based on specific matching conditions before applying a routing policy?

1) match statements
2) shutdown statements
3) reload statements
4) description statements

Correct Answer: 1) match statements

Explanation:
Route maps use match statements to identify which routes or packets should be affected by a particular policy. Conditions can include IP addresses, prefix lists, access lists, metrics, interfaces, or other routing attributes depending on the application. Once a route matches the required conditions, the route map can use set statements to modify attributes or behavior. Route maps are commonly used with policy-based routing, route redistribution, BGP policy, and other routing functions. Understanding the relationship between match and set is essential: match determines what traffic or routes are selected, while set determines what action is applied.

Q200. A router learns the same destination through multiple routing protocols. Which value is used first to determine which protocol’s route should be installed?

1) Metric
2) Hop count only
3) Administrative distance
4) Bandwidth

Correct Answer: 3) Administrative distance

Explanation:
Administrative distance is used to determine the relative trustworthiness of routes learned from different routing sources. When a router learns the same destination from multiple routing protocols, it generally prefers the route with the lower administrative distance before comparing protocol-specific metrics. For example, a route learned through OSPF and another learned through an external protocol can be evaluated using their administrative distances. Once a routing protocol has been selected, that protocol’s own metric is used to choose the best path among routes learned through that protocol. Understanding administrative distance is essential when troubleshooting unexpected route selection and designing backup routing paths.