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Q321. Which OSPF feature allows routes from one area to be summarized when they are advertised into another area?
1) Route summarization
2) Split horizon
3) Route reflection
4) NHRP
Correct Answer: 1) Route summarization
Explanation:
OSPF route summarization allows multiple specific routes to be represented by a single summary route, reducing the number of routes advertised between areas. Inter-area summarization is typically configured on an ABR, where routes from one area can be summarized before being advertised into another area. This can reduce routing-table size and limit the propagation of topology changes. Summarization is particularly useful in hierarchical OSPF designs because it helps isolate instability within an area. However, administrators must choose summary ranges carefully because an overly broad summary can attract traffic for destinations that do not actually exist.
Q322. Which OSPF command is commonly used to advertise a default route into an OSPF domain?
1) default-route advertise
2) default-information originate
3) redistribute default
4) ip ospf default
Correct Answer: 2) default-information originate
Explanation:
The OSPF default-information originate command allows a router to advertise a default route, represented as 0.0.0.0/0, into the OSPF routing domain. This is commonly used when one router provides Internet or upstream connectivity and other OSPF routers should send unknown destinations toward that router. By default, the router generally needs a default route in its own routing table before advertising it. The always keyword can be used when the administrator wants the router to advertise the default route even when a default route is not currently installed locally. Proper default-route advertisement is important in enterprise and service-provider edge designs.
Q323. What happens when an OSPF interface has a priority of zero on a broadcast network?
1) It becomes the DR immediately
2) It becomes the BDR immediately
3) It cannot participate in the DR/BDR election
4) It stops running OSPF
Correct Answer: 3) It cannot participate in the DR/BDR election
Explanation:
An OSPF interface priority of zero prevents that router from becoming either the Designated Router or Backup Designated Router on a broadcast or NBMA network. The router can still form OSPF neighbor relationships and exchange routing information normally. This is useful when an administrator wants to ensure that a particular router does not take the DR or BDR role, perhaps because the router has limited resources or is not intended to coordinate the multiaccess segment. Other routers with eligible priorities participate in the election. A priority of zero does not disable OSPF on the interface and does not prevent the router from learning or advertising OSPF routes.
Q324. Which OSPF state indicates that two routers have successfully exchanged database information and are maintaining a full adjacency?
1) Down
2) Init
3) 2-Way
4) Full
Correct Answer: 4) Full
Explanation:
The OSPF Full state indicates that two routers have completed the database exchange process and have synchronized their link-state databases. On point-to-point links, routers normally progress to Full when the adjacency is successfully established. On broadcast networks, routers form Full adjacencies with the DR and BDR, while relationships with other non-DR/non-BDR routers generally remain in the 2-Way state. If an expected adjacency remains stuck in ExStart, Exchange, or another intermediate state, troubleshooting should focus on issues such as MTU mismatches, packet loss, authentication problems, or incompatible OSPF parameters. The Full state therefore represents successful database synchronization.
Q325. Which EIGRP command can be used to prevent specific routes from being installed or advertised based on an access control list?
1) distribute-list
2) router-id
3) variance
4) passive-interface
Correct Answer: 1) distribute-list
Explanation:
An EIGRP distribute-list can be used to filter routing information based on specified criteria, commonly through an access control list or prefix list. It can control which routes are accepted from a neighbor or which routes are advertised to a neighbor. This provides administrators with more precise control over route propagation. For example, a network administrator can prevent a particular prefix from being advertised to a specific neighboring router without disabling the entire EIGRP relationship. Careful filtering is important because accidentally blocking essential routes can create connectivity problems. Route filtering should therefore be planned with a clear understanding of the direction and scope of the policy.
Q326. What is the purpose of an EIGRP query boundary?
1) To encrypt EIGRP packets
2) To limit the propagation of EIGRP queries
3) To elect an EIGRP leader
4) To increase the EIGRP hello interval
Correct Answer: 2) To limit the propagation of EIGRP queries
Explanation:
An EIGRP query boundary helps prevent queries from propagating unnecessarily throughout a large network. When an EIGRP route becomes Active and a router cannot immediately find a feasible successor, it may query neighboring routers for an alternate path. In poorly designed networks, these queries can spread widely and increase convergence time. Techniques such as EIGRP summarization and stub routing can help establish boundaries that limit query propagation. This improves scalability and reduces the likelihood of widespread Stuck-In-Active conditions. Proper EIGRP design therefore focuses not only on route selection but also on controlling the scope of topology queries.
Q327. Which EIGRP metric component represents the administrative preference for the reliability of a path?
1) Delay
2) Bandwidth
3) Reliability
4) Load
Correct Answer: 3) Reliability
Explanation:
EIGRP’s classic composite metric can consider bandwidth, delay, reliability, load, and MTU, although the default K values primarily use bandwidth and delay. Reliability represents the reliability of the path and is derived from interface measurements. While reliability is available as a metric component, it is not included in the default EIGRP metric calculation because the default K values give it no influence. Administrators should be cautious when modifying EIGRP metric coefficients because inconsistent K values between neighbors can prevent adjacency formation. Understanding the individual metric components is important when troubleshooting unexpected EIGRP path selection or designing advanced routing policies.
Q328. Which BGP attribute is generally considered when choosing between routes learned from different external neighbors and prefers a shorter AS_PATH?
1) AS_PATH
2) MED
3) Community
4) Originator ID
Correct Answer: 1) AS_PATH
Explanation:
The BGP AS_PATH attribute records the autonomous systems through which a route has passed. During BGP best-path selection, a shorter AS_PATH is generally preferred over a longer AS_PATH when the relevant earlier attributes are equal. AS_PATH also serves an important loop-prevention function because a BGP router normally rejects a route if its own AS number already appears in the path. Administrators can deliberately influence inbound traffic by using AS-path prepending to make a particular route appear less attractive to neighboring autonomous systems. Therefore, AS_PATH serves both a routing-policy purpose and a fundamental loop-prevention purpose in BGP.
Q329. Which BGP mechanism allows a router to request updated routing information without tearing down an established BGP session?
1) Route refresh
2) TCP reset
3) Session restart
4) Neighbor shutdown
Correct Answer: 1) Route refresh
Explanation:
BGP Route Refresh allows a router to request that a neighbor resend its routing information without resetting the established BGP session. This is especially useful after changing inbound routing policies. Instead of performing a disruptive hard reset, the router can request the relevant routes again and apply the updated policy. Route Refresh therefore reduces the operational impact of policy changes and helps maintain stable BGP sessions. It is preferable to repeatedly resetting BGP sessions when supported by the peers. Administrators can inspect neighbor capabilities and session behavior using BGP operational commands when troubleshooting route-policy changes and route refresh operations.
Q330. What is the primary advantage of BGP soft reset using inbound policy refresh mechanisms?
1) It permanently deletes all BGP routes
2) It applies changed policies without unnecessarily terminating the BGP session
3) It changes the remote AS number
4) It disables route advertisements
Correct Answer: 2) It applies changed policies without unnecessarily terminating the BGP session
Explanation:
A BGP soft reset allows routing policies to be changed and reapplied without completely tearing down the BGP session. This is operationally safer than performing a hard reset because the TCP connection and BGP relationship can remain established. Modern implementations commonly use Route Refresh to request the necessary routes again from the neighbor. Soft policy refresh is particularly useful when administrators modify inbound route maps, prefix lists, or other filtering policies and need the new rules to take effect. It reduces unnecessary service disruption and helps maintain stable routing operations while allowing administrators to validate the results of policy changes.
Q331. Which MPLS operation removes the top label from a packet before it reaches the egress PE?
1) Push
2) Swap
3) Pop
4) Rewrite
Correct Answer: 3) Pop
Explanation:
An MPLS pop operation removes an MPLS label from the packet. In many MPLS networks, Penultimate Hop Popping (PHP) allows the router immediately before the egress PE to remove the outer transport label. This means the egress PE does not need to perform an additional lookup to remove that transport label before processing the remaining information. PHP can improve efficiency by reducing label-processing work at the egress edge. MPLS also uses other operations, such as push when adding a label and swap when replacing one label with another. Understanding these operations is essential when troubleshooting MPLS forwarding behavior.
Q332. Which command displays the labels and forwarding information maintained by an MPLS-enabled router?
1) show mpls forwarding-table
2) show ip bgp vpnv4
3) show ip nhrp
4) show crypto session
Correct Answer: 1) show mpls forwarding-table
Explanation:
The show mpls forwarding-table command displays the MPLS Label Forwarding Information Base and provides information about how labeled packets are forwarded. It can show local labels, incoming labels, outgoing labels, next-hop information, and forwarding actions such as swapping or popping labels. This command is particularly useful when troubleshooting an MPLS forwarding problem because it allows administrators to verify whether the expected label operations exist. Additional commands may be required to inspect the underlying LDP neighbors or routing table. However, the forwarding table provides a direct view of how the router handles MPLS-labeled traffic.
Q333. Which command is most useful for verifying active NHRP mappings on a DMVPN router?
1) show ip ospf database
2) show ip nhrp
3) show ip bgp summary
4) show mpls ldp neighbor
Correct Answer: 2) show ip nhrp
Explanation:
The show ip nhrp command displays NHRP information, including mappings between tunnel addresses and NBMA addresses. This is especially useful when troubleshooting DMVPN connectivity because NHRP is responsible for resolving the logical tunnel addresses of remote peers to their underlying transport addresses. If expected mappings are missing or incorrect, direct spoke-to-spoke communication may fail in DMVPN designs that depend on dynamic NHRP resolution. Administrators can use this command together with show dmvpn and routing-table commands to determine whether the problem is related to NHRP registration, routing, or the underlying tunnel configuration.
Q334. Which DMVPN phase supports direct spoke-to-spoke tunnels while maintaining the original spoke routes learned through the hub?
1) Phase 1
2) Phase 2
3) Phase 0
4) Phase 4
Correct Answer: 2) Phase 2
Explanation:
DMVPN Phase 2 allows spokes to establish direct spoke-to-spoke communication while preserving the original routing next-hop information needed for those direct paths. NHRP is used to resolve the remote spoke’s NBMA address, allowing the source spoke to create a direct dynamic tunnel. The routing design is important because the spoke must learn routes with an appropriate next hop that allows it to resolve the destination spoke directly. Phase 1 generally forces spoke traffic through the hub, while Phase 3 introduces additional NHRP shortcut behavior that can simplify routing designs. Understanding these differences is essential when selecting the appropriate DMVPN phase for a network.
Q335. Which IPsec protocol provides encryption, authentication, integrity, and anti-replay protection for IP traffic?
1) ESP
2) AH
3) GRE
4) NHRP
Correct Answer: 1) ESP
Explanation:
IPsec Encapsulating Security Payload, or ESP, can provide confidentiality through encryption as well as integrity, authentication, and anti-replay protection. ESP is widely used for site-to-site VPNs because it can protect the contents of transmitted IP packets while allowing secure communication across untrusted networks. Authentication Header, or AH, can provide integrity and authentication but does not provide encryption. GRE is an encapsulation protocol rather than an encryption protocol, while NHRP is used for address resolution in technologies such as DMVPN. In practical VPN deployments, ESP is frequently combined with IKE, which negotiates security parameters and establishes the cryptographic framework.
Q336. Which IKE version is commonly preferred for modern IPsec VPN deployments because of improved negotiation capabilities and flexibility?
1) IKEv1 only
2) IKEv2
3) GREv2
4) ESPv2
Correct Answer: 2) IKEv2
Explanation:
IKEv2 is widely used for modern IPsec VPN deployments because it provides a more streamlined negotiation process and several improvements over IKEv1. It supports stronger and more flexible authentication and provides mechanisms for handling mobility, reliability, and reauthentication more effectively. IKE itself does not encrypt user data directly; instead, it negotiates security associations and establishes the parameters that IPsec uses to protect traffic. Once the necessary security associations are established, protocols such as ESP protect the actual data. When troubleshooting an IKEv2 VPN, administrators commonly examine IKE security associations, IPsec security associations, proposals, authentication, and peer reachability.
Q337. Which HSRP configuration allows a router to reclaim the Active role after recovering from a failure when it has the highest priority?
1) standby preempt
2) standby shutdown
3) standby track disable
4) standby authentication none
Correct Answer: 1) standby preempt
Explanation:
The HSRP standby preempt command allows a router with a higher HSRP priority to take over the Active role after it becomes available again. Without preemption, another router that assumed the Active role during the failure may continue operating as Active even after the preferred router recovers. Preemption is therefore commonly configured when administrators want a specific router to be the normal active gateway. HSRP priority determines which router is preferred, while preemption determines whether that preferred router can reclaim the Active role. This is particularly useful when the preferred router has superior uplink connectivity or hardware resources.
Q338. Which IPv6 mechanism allows hosts to automatically obtain addressing information from router advertisements without requiring a DHCPv6 server for address assignment?
1) NAT64
2) SLAAC
3) NHRP
4) HSRP
Correct Answer: 2) SLAAC
Explanation:
IPv6 Stateless Address Autoconfiguration, or SLAAC, allows hosts to automatically configure IPv6 addresses using information provided through Router Advertisement messages. The router advertisement can contain the network prefix and other configuration parameters, allowing a host to construct its own interface identifier and form a usable IPv6 address. This eliminates the requirement for a DHCPv6 server when only stateless address configuration is needed. SLAAC is commonly used alongside IPv6 Neighbor Discovery. DHCPv6 can still be used when administrators need additional configuration information or stateful address assignment. Understanding the flags contained in Router Advertisement messages helps determine how hosts obtain their IPv6 configuration.
Q339. Which IPv6 protocol message is sent by a host to discover routers on its local network?
1) Router Solicitation
2) Router Advertisement
3) Neighbor Advertisement
4) Echo Reply
Correct Answer: 1) Router Solicitation
Explanation:
An IPv6 host sends a Router Solicitation message when it wants to discover available routers on the local network. Router Solicitation is part of IPv6 Neighbor Discovery and uses ICMPv6. Routers receiving the solicitation can respond with Router Advertisement messages containing information such as network prefixes, configuration flags, and other parameters. Hosts can also receive unsolicited Router Advertisements periodically, but Router Solicitation allows a host to actively request the information instead of waiting. This process is important for SLAAC and IPv6 default-router discovery. Troubleshooting IPv6 connectivity should therefore include checking whether Router Solicitations and Router Advertisements are being exchanged correctly.
Q340. Which IP SLA feature can automatically influence routing behavior when a monitored destination becomes unreachable?
1) Object tracking
2) BGP communities
3) MPLS PHP
4) OSPF DR election
Correct Answer: 1) Object tracking
Explanation:
IP SLA can actively monitor network conditions such as reachability, latency, or response time, while object tracking can use the IP SLA result to influence other configuration elements. For example, a router can track whether an important remote destination is reachable and modify a static route or HSRP priority when the tracked object changes state. This allows the network to respond dynamically to failures instead of relying only on physical interface status. A common design uses an IP SLA probe to test an upstream destination, an object-tracking statement to monitor the probe, and a routing or first-hop redundancy mechanism to react when the test fails.