Cisco CCNP 300-410 ENARSI Practice Questions with Explanations

Correct answer: B

The branch network users cannot reach the Internet because R1 is configured as an EIGRP stub router, which by default does not advertise routes learned from other neighbors. Since R1 is the gateway between the branch (2001:db8:0:4::/64) and the rest of the network (R2 and the Internet), the stub configuration prevents R1 from advertising the default route or Internet routes to the branch. The 'no eigrp stub' command on R1 removes the stub designation, allowing R1 to advertise all learned routes including the Internet path via R2, restoring connectivity for branch users.

Why the other options are wrong:

• A. Issuing 'eigrp stub' on R1 would further restrict routing and worsen the problem, not solve it.
• C. R2 is the Internet gateway and does not need stub configuration; the issue originates at R1 blocking route advertisements.
• D. Removing stub from R2 would not help because R2 is not the problematic router; R1 is the blocking point for branch traffic.

Correct answer: A

The route-map OUT command uses 'set as-path prepend 65000' which adds AS 65000 to the beginning of the AS-PATH attribute before advertising the prefix 192.168.130.0/24 to eBGP neighbor R1. This causes R1 to see the route as originating from an additional AS hop away, making the AS-PATH length appear as two hops instead of one. The AS-PATH is used by BGP for path selection, so R1 will perceive this locally originated prefix as coming through an extra autonomous system.

Why the other options are wrong:

• B. The route-map only manipulates the AS-PATH attribute of 192.168.130.0/24; it does not filter other routes or prevent their acceptance at R1.
• C. AS-PATH prepending affects route selection metrics but does not block traffic forwarding; R1 will still forward traffic to 192.168.130.0/24 if it is the best path.
• D. AS-PATH prepending makes the route less preferred but does not prevent it from entering the routing table; R1 will still accept and store the route in its BGP table.

Correct answer: C

Policy-based routing (PBR) allows a router to make forwarding decisions based on policies and criteria other than just the destination IP address, without modifying the routing table itself or the IP data plane routing logic. It intercepts packets and applies match-action rules to redirect them independently of normal routing table lookups.

Why the other options are wrong:

• A. Nonbroadcast multiaccess (NBMA) describes a network topology type, not a forwarding decision method.
• B. Packet switching is the general process of forwarding packets, not a method that changes forwarding decisions outside the routing table.
• D. The Forwarding Information Base (FIB) is derived from and depends on the routing table, so changes to forwarding via FIB involve routing table changes.

Correct answer: C

In the exhibit, the route to 192.168.2.2[110/11] is shown as reachable via 192.168.12.2 through OSPF (evidenced by the metric notation [110/11] where 110 is OSPF's default AD). The static route that was configured for this destination is being overridden because the static route has a higher Administrative Distance than OSPF. When multiple routes exist to the same destination, the routing protocol with the lower AD value is preferred. Since OSPF has an AD of 110 and static routes have a default AD of 1 (or whatever was configured higher than 110), the OSPF route is being selected instead of the configured static route.

Why the other options are wrong:

• A. Dynamic routing protocols do not automatically have priority over static routes; the deciding factor is Administrative Distance, not protocol type.
• B. While OSPF metric values matter within OSPF routing decisions, the primary reason a different next hop is chosen is the lower AD of OSPF compared to the static route's higher AD.
• D. If the syntax were invalid, the static route would simply not appear in the routing table at all; the fact that a different route is chosen indicates the static route exists but is being deprioritized due to AD.

Correct answer: C

The summary-address command in OSPF only generates and advertises a summary route if at least one subnet within that summary range exists in the OSPF routing table or database. In this case, looking at the routing table output, there are no routes for any subnets within the 10.0.0.0/8 range. The existing routes are for 192.168.x.x networks only. Since there are no component subnets of 10.0.0.0/8 being learned or advertised through OSPF, the router has no reason to generate the summary route, and therefore it does not appear in the routing table.

Why the other options are wrong:

• A. The summary-address command is specifically used for inter-area route summarization at Area Border Routers (ABRs), which is a valid OSPF function, so this statement is misleading; the real issue is the absence of component routes.
• B. OSPF summary routes generated by summary-address commands do appear in the routing table when they are actually created; the issue here is that the summary route is not being generated at all due to missing component routes.
• D. Summary routes created at one router with the summary-address command are advertised to other routers in the domain; if the route doesn't exist, it won't appear anywhere, not just on this router.

Correct answer: D

Add this statement to the route map: route-map RM- OSPF-DL deny 20. The route-map RM-OSPF-DL is currently applied to distribute OSPF routes with a permit at sequence 10. To block a route from being redistributed into the routing table, a deny statement must be added to the route-map with a sequence number that matches before the permit. Adding 'route-map RM-OSPF-DL deny 20' creates a catch-all deny clause that prevents routes not matching earlier specific criteria from being redistributed. Since the permit at sequence 10 only matches access-list 1 (which matches 192.168.2.2 specifically), any subsequent sequences would not affect that route. However, the correct interpretation is that a deny sequence needs to be added to explicitly block the route before the permit clause, or the route-map structure needs to prevent the 192.168.2.2 prefix from being permitted. Option D adds an explicit deny that would block routes in the redistribution process.

Why the other options are wrong:

• A. Extended access lists provide more granular matching than standard lists, but would not change the permit behavior already in place at sequence 10.
• B. Changing sequence 10 from permit to deny would block the route from redistribution, but since no routes are currently being matched (0 packets, 0 bytes), this indicates the route-map is not actually filtering the OSPF route being advertised into the routing table.
• C. While prefix lists are generally preferred over access lists for route filtering, this change alone does not address the fundamental issue that the route-map needs to explicitly deny the route rather than permit it.

Correct answer: C

Cisco Express Forwarding (CEF) must be enabled on all participating BFD endpoints because BFD relies on CEF's fast switching and efficient packet handling to detect failures rapidly and accurately. CEF provides the underlying forwarding infrastructure that BFD depends on.

Why the other options are wrong:

• A. Jumbo frame support is not a prerequisite for BFD; BFD works with standard frame sizes.
• B. Only the two BFD endpoints need BFD enabled; intermediate routers in the path do not require BFD configuration.
• D. The timers 3 9 command is not a prerequisite; BFD can be configured with BGP using default or custom timers without this specific command being mandatory.

Correct answer: A

Looking at the exhibit, R2 (the route reflector) learns the route 172.16.25.0/24 from R1 with next hop 209.165.200.225. However, examining R2's BGP table, the route shows a Weight of 100 and is marked with an asterisk (*) and 'i' indicator, suggesting it's an internal route. The critical issue is that R2 does not have a valid route to reach the next hop 209.165.200.225 in its routing table. In BGP, a route reflector will not advertise a prefix to other clients if it cannot itself reach the next hop address. This is a fundamental BGP behavior-the route must be valid and reachable for the router to propagate it. Without a route to the next hop, R2 cannot advertise this prefix to its other client, R3.

Why the other options are wrong:

• B. Route reflector setup explicitly eliminates the requirement for full IBGP mesh; that's the entire purpose of route reflectors-to reduce mesh complexity.
• C. BGP advertises both classful and classless prefixes regardless of route reflector configuration; classfulness is not a filtering criterion in route reflector setups.
• D. Route reflectors specifically exist to advertise prefixes from one client to another; this is their core function. The rule is that routes from clients ARE reflected to other clients (except back to the originating client).

Correct answer: D

By default, when redistributing OSPF routes into BGP, only internal OSPF routes (intra- area and inter-area routes with metric 0) are redistributed. External OSPF routes (Type 1 and Type 2 external routes) are not redistributed by default. In the exhibit, the show ip bgp output displays routes with metrics of 0 and 20, and the 192.168.3.0/24 route shows a metric of 20 via 192.168.12.2, indicating these are the internal routes being redistributed. To redistribute external OSPF routes as well, the engineer would need to use the 'redistribute ospf 1 match external' command to explicitly include external routes in the redistribution policy.

Why the other options are wrong:

• A. This statement is backwards; by default internal routes are redistributed, not external type 1 routes
• B. OSPF redistribution is not limited to classful networks; classless (CIDR) networks are also redistributed
• C. BGP convergence speed is not the issue; the routes are either redistributed or they are not based on the redistribution policy

Correct answer: D

A BGP neighbor transitions to the Idle state when the maximum prefix limit is exceeded. When a BGP peer sends more prefixes than the configured maximum limit (max-prefix), the router resets the connection and returns the neighbor to Idle state as a protective mechanism to prevent route table exhaustion. This is a standard BGP safeguard that disconnects the neighbor when the threshold is breached, contrasting with simply rejecting individual prefixes when at the limit.

Why the other options are wrong:

• A. Not receiving prefixes would not cause the neighbor to enter Idle; the neighbor would remain in Established state even with zero prefixes received.
• B. Reaching the maximum limit (not exceeding it) does not trigger Idle state; the neighbor remains Established and simply stops accepting additional prefixes.
• C. Applying an inbound prefix list filters prefixes but does not change neighbor state; the neighbor remains Established while the list silently rejects non-matching routes.

Correct answer: A

Shared Risk Link Group (SRLG) disjoint ensures that the primary path and the loop-free alternate path do not share any common risk, such as links connected through the same fiber bundle or physical infrastructure. This eliminates LFAs that would fail simultaneously with the primary path due to shared physical resources.

Why the other options are wrong:

• B. Linecard-disjoint refers to ensuring paths use different linecards, which is less comprehensive than SRLG for handling common fiber dependencies.
• C. Lowest-repair-path-metric is a metric for selecting among LFAs, not an attribute that eliminates LFAs based on shared risks.
• D. Interface-disjoint only ensures different interfaces are used but does not account for common physical infrastructure like shared fiber.

Correct answer: D

The exhibit shows log entries with timestamps that don't match the device's clock (shown as 15:42:00.506 CET). The question asks which action ensures consistency between the clock on the device and the timestamps of log entries. While options A and C control the format of timestamps in logs (uptime vs. datetime/localtime), they do not actually synchronize the device's internal clock with the correct time. Option B is not a valid Cisco command. Option D-synchronizing the device clock with an NTP server-ensures that the device's actual system clock is accurate, which will cause all subsequent log entries to display timestamps that match the true time. This directly resolves the discrepancy between the clock and log entry times.

Why the other options are wrong:

• A. This command changes timestamp format to uptime but does not synchronize the actual clock; the device clock remains out of sync with real time.
• B. The command 'logging clock synchronize' is not a valid Cisco IOS command for time synchronization.
• C. This command changes timestamp format to datetime/localtime but does not synchronize the actual device clock; the underlying time remains incorrect.

Correct answer: C

The configuration shows a service-policy applied to the control plane with a class-map for BGP that matches traffic by access-group name 'BGP' and applies a 'drop' action. This means any BGP traffic that matches the access list named 'BGP' will be dropped, preventing BGP neighborships from forming with devices matched by that access list. The class-default with match-any permits other traffic, but the BGP class explicitly drops matched traffic.

Why the other options are wrong:

• A. The configuration actively drops BGP traffic matching the access list, so neighborships cannot form with all devices.
• B. The router can still form BGP neighborships with devices not matched by the access list, as only the matched traffic is dropped.
• D. The policy drops traffic matching the BGP access list, preventing neighborships with those matched devices, not allowing them.

Correct answer: B

The command 'show ip route vrf' displays the IP routing table for a specific VRF instance in VRF-Lite configurations. This command allows viewing routes associated with a particular VRF namespace.

Why the other options are wrong:

• A. The 'show ip vrf' command displays VRF configurations and their properties, not the routing table entries.
• C. The 'show run vrf' command displays the running configuration for VRF, not routing table information.
• D. The 'show ip protocols vrf' command displays routing protocol information within a VRF, not the routing table itself.

Correct answer: A

The diagram shows R2 performing redistribution between RIP (yellow area) and EIGRP (green area) at IP 12.12.12.0/24, and R2 also performing redistribution between EIGRP and OSPF at the interface connecting to R3. The configuration on R3 shows prefix-list OSPF-TAG-PRF denying 10.1.0.0/16 and OSPF-TAG-PRF-1 permitting 10.2.0.0/18. The route-map OSPF-TAG-1 uses these prefix-lists to control redistribution. The subnet 10.2.2.0/24 falls within the 10.2.0.0/18 range that is permitted by OSPF-TAG-PRF-1 and therefore allowed through to OSPF, making it the subnet that is redistributed from EIGRP to OSPF.

Why the other options are wrong:

• B. 10.1.4.0/26 falls within 10.1.0.0/16 which is explicitly denied by OSPF-TAG-PRF, preventing its redistribution to OSPF.
• C. 10.1.2.0/24 falls within 10.1.0.0/16 which is explicitly denied by OSPF-TAG-PRF, preventing its redistribution to OSPF.
• D. 10.2.3.0/26 falls within the 10.2.0.0/18 permitted range but the diagram specifically shows 10.2.2.0/24 as the subnet being redistributed based on the configuration logic.

Correct answer: D

The command 'router ospfv3 1 address-family ipv4 unicast' correctly enters the OSPFv3 address family configuration mode for IPv4 unicast routing. This syntax properly configures OSPFv3 to support IPv4 address families in addition to its native IPv6 support.

Why the other options are wrong:

• A. This command enters address family mode but is incomplete; it does not specify the unicast keyword required for proper configuration.
• B. This command uses invalid syntax; 'ospfv3' is a routing process command, not a configuration that belongs at the global level with this structure.
• C. While this appears to enter an interface, this syntax is incorrect for OSPFv3 address family configuration; interfaces must be enabled within the address family context after proper setup.

Correct answer: B

The configuration shows that R1 is redistributing RIP subnets into OSPF with a route-map called ADD. The route-map ADD has a permit statement with tag 1 set. When a route-map sets a tag during redistribution, that tag value is applied to the redistributed routes. Therefore, RIP learned routes are being distributed to OSPF with a tag value of one assigned by the route-map.

Why the other options are wrong:

• A. The tag is set ON the routes being redistributed, not used as a filter condition to permit redistribution; routes are redistributed regardless of whether they have a tag of one.
• C. Setting a tag value does not modify the metric of routes; tags are attributes used for route identification and policy, not metric manipulation.
• D. RIP routes are not redistributed without changes; the route-map explicitly sets a tag value of one on the redistributed routes, which is a change to the route attributes.

Correct answer: C

When an IP SLA is configured to monitor reachability and modify routing behavior, the actual route changes and failover events are tracked within the routing system. The 'debug ip routing' command displays routing table updates, route installation/removal, and routing decisions in real-time. This is the appropriate debug command to observe when the default route changes from pointing through R3 (via R1's Fa0/0) to pointing through R2 (via R1's Fa0/1) due to SLA-detected reachability loss. The other commands target different layers of packet processing or SLA-specific errors rather than the routing table modifications.

Why the other options are wrong:

• A. debug ip flow displays NetFlow information about traffic flows, not routing table changes or SLA-triggered route modifications
• B. debug ip sla error shows SLA-specific error messages but does not display the routing table updates that result from SLA-triggered failover events
• D. debug ip packet traces individual packet forwarding but is too low-level and does not show routing table changes or SLA decision logic

Correct answer: C

The correct sequence is: first create the VRF named 'Inet' with 'ip vrf Inet', then enter the interface configuration mode, and finally bind the interface to the VRF using 'ip vrf forwarding Inet'. This is the proper two-step process for assigning an interface to a VRF.

Why the other options are wrong:

• A. The syntax 'ip vrf FastEthernet0/0' is invalid; you cannot assign an interface to a VRF at the VRF configuration level in this way.
• B. This syntax is invalid; the interface name cannot be specified directly in the 'ip vrf' command at the global config level.
• D. This mixes OSPF routing configuration with VRF assignment; 'ip vrf forwarding' does not belong in router OSPF context, and this is not the correct method for interface-to- VRF binding.

Correct answer: A

The issue is that after redistribution is enabled, PC2, PC3, and PC4 cannot reach PC1 (which is connected to R1). The problem occurs because R2 is learning about 10.1.1.0/24 via both RIP (from R1 at AD 120) and redistributed routes, but the redistributed routes from EIGRP/OSPF back to RIP may have lower administrative distances or cause routing loops. By setting the administrative distance to 100 under the RIP process on R2, the RIP routes become more preferred (AD 100 < AD 120 default), ensuring that R2 prefers the direct RIP route to 10.1.1.0/24 from R1 over any redistributed paths. This prevents the routing loop and allows proper reachability to PC1.

Why the other options are wrong:

• B. Filtering 10.1.1.0/24 during OSPF to EIGRP redistribution would prevent the EIGRP domain from learning this route, making it unreachable to PC4 and defeating the goal of connectivity.
• C. Filtering 10.1.1.0/24 during RIP to EIGRP redistribution would prevent proper route propagation to the EIGRP domain, leaving PC3 and PC4 unable to reach PC1.
• D. Redistributing directly connected interfaces on R2 is unnecessary and would not solve the core issue of administrative distance causing suboptimal routing or routing loops in the current topology.

Correct answer: D

In BGP path selection, weight is the first attribute evaluated (highest preference wins). The configuration shows a weight of 200 being set for AS 690 routes from neighbor 10.222.1.1 via the route map. If traffic is still being sent to a different neighbor for AS 690 routes, that neighbor must have a weight value higher than 200, which would cause BGP to prefer that path despite the route map configuration on 10.222.1.1. Weight is evaluated before local preference in the BGP decision process, so a higher weight at another neighbor would override the local preference and weight settings shown here.

Why the other options are wrong:

• A. Local preference is evaluated after weight in BGP path selection, so a higher local preference at another neighbor would not override a weight of 200 already set on 10.222.1.1.
• B. The local preference value (250) being different from weight (200) is not the issue; these are separate attributes and both can be set independently without causing the problem described.
• C. The route map direction (in vs out) is correctly applied here; the issue is not directional but rather that another neighbor has a higher-priority attribute value.

Correct answer: C

EIGRP adjacency requires that both routers actively send and receive EIGRP hello packets on the connecting interface. R1 does not have a passive-interface command on FastEthernet0/0, meaning it actively sends EIGRP packets. R2 has 'passive-interface FastEthernet0/0' configured, which prevents it from sending and receiving EIGRP hello packets on that interface. This mismatch prevents adjacency formation. Removing the passive-interface command from R2 allows it to actively participate in EIGRP on that interface, matching R1's configuration and enabling adjacency to be established.

Why the other options are wrong:

• A. Both routers are already configured with the same EIGRP autonomous system number (100), so changing it would make the problem worse, not better.
• B. Adding passive-interface to R1 would prevent both routers from sending hellos, making adjacency impossible rather than fixing it.
• D. The no auto-summary command affects route summarization behavior, not EIGRP neighbor adjacency formation.

Correct answer: D

When using the 'set ip default next-hop' command in policy-based routing, packets matching the policy are forwarded to the specified next hop regardless of whether the destination IP exists in the routing table. The 'default' next-hop serves as an explicit forwarding target for matched packets.

Why the other options are wrong:

• A. Packets are not dropped; the policy explicitly directs them to the specified next hop.
• B. Packets are not forwarded based on the routing table; the policy overrides normal routing table lookup with the default next-hop.
• C. Packets follow the policy-specified next-hop, not a static route; static routes are separate from PBR policy actions.

Correct answer: D

The configuration shows a prefix list named DefaultRouteOnly that is being distributed out of Tunnel0. Sequence 5 denies 0.0.0.0/0 (the default route), while sequence 10 permits 0.0.0.0/0. Since sequence 5 comes first and denies the default route, the deny statement blocks the default route from being advertised before sequence 10 can permit it. The administrator's goal is to advertise only the default route to the remote low-resources router, so removing sequence 5 allows sequence 10's permit statement to take effect, enabling default route advertisement.

Why the other options are wrong:

• A. Removing the prefix keyword would break the distribute-list syntax and prevent any filtering from working; the prefix keyword is required for prefix list-based distribution.
• B. Removing sequence 10 would leave only the deny statement, preventing all routes including the default route from being advertised, which is the opposite of what is needed.
• C. Changing the direction from out to in would affect inbound route filtering on the remote router rather than outbound advertisement from this router, failing to resolve the advertisement issue.

Correct answer: B

The configuration shows OSPFv3 4 area 0 ipv4 is applied to the E 0/0 interface, which means only the IPv4 address family is being advertised under OSPFv3. To bring up IPv6 OSPF neighbors on the E 0/0 interface, the IPv6 address family must be enabled under the router ospfv3 4 process using the address-family ipv6 unicast command (or equivalently, the ipv4 address family configuration needs to be changed to support IPv6). The neighboring router is fully configured, so the branch router's OSPFv3 process is not advertising the IPv6 route properly because it only has the IPv4 address family active. Enabling the IPv4 address family at the process level (option B) allows the router to properly recognize and advertise both address families for OSPFv3 neighbor establishment.

Why the other options are wrong:

• A. Disabling OSPFv3 IPv4 entirely would remove routing functionality rather than fix the IPv6 neighbor relationship; the issue is not that IPv4 is running but that IPv6 is not properly enabled.
• C. Disabling IPv6 on the interface would prevent IPv6 OSPF neighbors from forming, which is the opposite of the goal.
• D. The address-family command at the interface level is not how OSPFv3 address families are configured; they are configured at the router process level under the router ospfv3 command.

Correct answer: A

R2 has two paths to 192.168.13.0/24: one through R3 with composite metric 1075200, and one through R1 with composite metric 2611200. Currently only the lowest metric path (through R3) is used. To enable unequal cost load balancing in EIGRP, the variance command must be configured. The variance multiplier determines which routes are considered feasible for load balancing. The current metric ratio is 2611200/1075200 ≈ 2.43, so a variance of 4 would include both paths (since 1075200 × 4 = 4300800 > 2611200), enabling traffic to use both paths.

Why the other options are wrong:

• B. Configuring bandwidth on an interface affects metric calculation but does not enable unequal cost load balancing; variance is required for that.
• C. Configuring delay on an interface affects metric calculation but does not enable unequal cost load balancing; variance is required for that.
• D. A variance of 2 would result in a feasible distance of 1075200 × 2 = 2150400, which is less than the alternative path metric of 2611200, so the second path would still not be included in load balancing.

Correct answer: D

The log shows repeated DBD (Database Description) retransmissions followed by the neighbor transitioning from EXSTART to DOWN state due to 'Too many retransmissions.' This pattern indicates the routers cannot successfully exchange database descriptions, which is a classic symptom of MTU mismatch. When MTU values differ between neighbors, the larger DBD packets cannot be properly transmitted and acknowledged, causing retransmission attempts to fail and the adjacency to collapse. Matching MTU values between the neighbors is required to restore the OSPF adjacency.

Why the other options are wrong:

• A. Hello timers being mismatched would prevent adjacency formation initially, but the log shows the neighbors did establish contact (EXSTART state was reached), indicating hello timers are already matching.
• B. OSPF is already configured and running on both routers, as evidenced by the DBD exchanges and adjacency state transitions shown in the log.
• C. Router IDs are used for neighbor identification and would affect adjacency formation, but the routers have successfully reached the EXSTART state, meaning router IDs are not the issue here.

Correct answer: D

LOCAL_PREF (Local Preference) is the appropriate BGP attribute to prefer one ISP link over another within the same AS. By configuring a higher LOCAL_PREF value for the low- delay ISP link, the router will prefer that path and avoid the high-delay link when both routes are available.

Why the other options are wrong:

• A. AS-PATH influences route selection based on AS path length, not link quality or delay characteristics.
• B. WEIGHT is a Cisco-specific attribute that works only locally on a single router and is less suitable for multi-router BGP scenarios than LOCAL_PREF.
• C. MED (Multi-Exit Discriminator) is used to influence route selection from external AS perspectives and is primarily for incoming route preferences, not preferred outgoing link selection.

Correct answer: D

The question states that a default static route (0.0.0.0 0.0.0.0 pointing to 99.3.5.1) needs to be redistributed into OSPF so internal routers can reach the Internet. The command `default-information originate` is the proper OSPF command that advertises a default route (0.0.0.0/0) to all OSPF neighbors. This is the standard method for propagating a default route within an OSPF domain when the router has connectivity to an external network like the Internet. Option D correctly restores Internet reachability by ensuring the default route is advertised as an OSPF external route type 2 (E2) throughout the OSPF area.

Why the other options are wrong:

• A. While `redistribute static subnets` can redistribute static routes, it requires the specific static route to be defined and does not automatically handle the default route 0.0.0.0/0 without additional configuration.
• B. The `network 0.0.0.0 0.0.0.0 area 0` command does not redistribute routes; it advertises directly connected networks into OSPF, which is not applicable for advertising an external default route to the Internet.
• C. The `redistribute connected` command redistributes directly connected networks into OSPF, not static routes, and does not properly advertise the default static route pointing to the ISP.

Correct answer: B

To isolate the Math and Science departments while allowing them to connect through the IT router, Virtual Routing and Forwarding (VRF) must be implemented. The Science department devices (connected via e0/2 and e0/3) need to be placed in a separate VRF from the Math department (default VRF). Option B correctly defines a VRF named 'Science' and then applies the 'vrf forwarding Science' command to both interfaces e0/2 and e0/3 before assigning IP addresses. This ensures that traffic from the Science department is isolated in its own routing table, preventing it from reaching the Math department which remains in the default VRF. The vrf forwarding command must be executed on the interface configuration before the IP address is assigned.

Why the other options are wrong:

• A. Defines the VRF but never applies it to any interfaces using 'vrf forwarding', so both departments remain in the default VRF with no isolation achieved.
• C. Attempts to apply 'vrf forwarding' after the IP address command, which is incorrect syntax and violates the proper command sequence (vrf forwarding must precede the IP address assignment).
• D. Only defines the VRF but never applies it to the interfaces, leaving both departments in the default VRF without any isolation between Math and Science departments.

Correct answer: D

The route map EIGRP->OSPF uses 'match ip address' statements with three prefix lists (WAN_PREFIXES, LOCAL_PREFIXES, VPN_PREFIXES), but the match statements are missing the 'prefix-list' keyword. Without this keyword, the match command cannot properly evaluate the prefix list entries. The syntax should be 'match ip address prefix-list WAN_PREFIXES' instead of 'match ip address WAN_PREFIXES'. This is why the redistribution is failing-the route map conditions are not being properly evaluated against the defined prefix lists.

Why the other options are wrong:

• A. The 10.0.106.0/24 network is defined in the EIGRP network statement and doesn't need to exist in the prefix lists; the issue is with the route map syntax, not the prefix list contents.
• B. Using the network statement versus redistribute command in EIGRP doesn't affect the route map matching process; both would require proper route map evaluation.
• C. While a default metric is typically needed when redistributing, this is not the root cause of the match failure shown in the configuration.

Correct answer: C

In a route reflector topology, route reflectors forward routes between clients and non- clients, but regular iBGP peers require full mesh connectivity or route reflection to exchange routes. Currently, R2 and R5 are configured as route reflectors. R1 is a client of R2, and R4 appears to be a non-reflector peer. The problem is that R4 and R6 cannot communicate all routes because R4 is not a route reflector and sits in a position where it needs to reflect routes between different clusters. Additionally, R1 cannot advertise all routes to eBGP peers (R3 and R7) without complete route visibility. By configuring R4 as a route reflector, it can reflect routes within the AS 64512 topology to R1. R5 must remain a route reflector to maintain the existing reflection path. This configuration ensures all internal routes are visible throughout the AS before being advertised to external peers.

Why the other options are wrong:

• A. R1 should not be a route reflector since it is already acting as a client to reflect routes to external eBGP peers; R4 alone cannot solve the complete connectivity problem.
• B. R1 should not be configured as a route reflector as it serves as the external advertisement point; R5 is already a route reflector.
• D. R2 is already configured as a route reflector; configuring it again adds no benefit. R4 is the critical missing route reflector for proper route advertisement to R1.

Correct answer: D

All Routers router ospf 1 auto-cost reference- bandwidth 1000 OSPF calculates interface cost using the formula: cost = reference_bandwidth / interface_bandwidth. The direct links between SanFrancisco and Boston operate at 100 Mbps, while the default reference bandwidth is 100 Mbps, yielding a cost of 1. The 1 Gbps links to Dallas have a cost of 0 (rounded down). For OSPF to prefer the direct 100 Mbps links over the 1 Gbps path through Dallas, the reference bandwidth must be increased to 1000 Mbps (1 Gbps). This makes the 100 Mbps direct links cost 10, while the 1 Gbps links cost 1, reversing the preference. Since this affects the entire OSPF domain's cost calculations, the command must be applied to all routers to ensure consistent routing decisions.

Why the other options are wrong:

• A. Setting reference bandwidth to 100 maintains the default, leaving the 100 Mbps links with cost 1 and 1 Gbps links with cost 0, so the slower path through Dallas remains preferred.
• B. Configuring only the SanFrancisco router creates inconsistent cost calculations across the OSPF domain; Boston would still use default reference bandwidth, causing routing loops or suboptimal paths.
• C. Configuring only the Boston router creates the same inconsistency problem as option B, with SanFrancisco using different cost calculations than Boston.

Correct answer: C

To ensure Branch B only uses the MPLS B network to reach HQ, we must make the MPLS B path more preferred than the MPLS A path. Local preference is the highest- priority BGP attribute in the decision process (checked before AS path length or weight). By increasing the local preference for HQ prefixes received via MPLS B to a value higher than those received via MPLS A, Branch B will always select MPLS B as the preferred path to HQ, regardless of other factors. Local preference is evaluated before weight in BGP's best path selection algorithm, making it the correct mechanism to enforce this routing policy.

Why the other options are wrong:

• A. AS path prepending on Branch A makes routes from Branch A less preferred, but does not directly influence Branch B's path selection between its two connections to HQ.
• B. Weight is a Cisco-specific attribute with lower priority than local preference; it does not follow the same standardized BGP decision process and would not reliably enforce the requirement across all scenarios.
• D. Filtering local prefixes on Branch A does not address how Branch B chooses between its two paths to HQ; it would not prevent Branch B from using MPLS A if that path became preferred for other reasons.

Correct answer: C

By default, when OSPF routes are redistributed into BGP, only OSPF internal routes (intra-area and inter-area) are redistributed. External routes (Type 1 and Type 2 external routes) are not redistributed unless explicitly specified. The command 'redistribute ospf 0.0.0.0 include internal external' adds the 'include internal external' keywords to ensure that both internal and external OSPF routes are redistributed into BGP, resolving the issue where not all OSPF routes appear in the BGP routing table.

Why the other options are wrong:

• A. Simply including the word 'external' without 'internal' would exclude internal routes and is incomplete syntax; the correct syntax requires both keywords with 'include'.
• B. A route-map is unnecessary; the solution does not require filtering by access list but rather enabling redistribution of all OSPF route types.
• D. A route-map with a prefix list adds unnecessary complexity; the direct 'include internal external' approach within the redistribute command is the correct and simpler solution.

Correct answer: B

The network shows mutual redistribution between EIGRP and BGP on R3 and R1, with R4 in AS64512 connected via BGP. The intermittent connectivity and significant routing update changes indicate a routing loop caused by mutual redistribution. Since R3 and R4 are in different AS domains, the BGP session between them is eBGP (AS64512 is external to the redistribution domain). The 10.1.1.0/24 network is being learned via both EIGRP (through R1) and BGP (through R4), creating competing paths. By reducing iBGP administrative distance from 200 to 100 on R3, BGP routes become more preferred over EIGRP routes in the local routing table, providing a stable path preference and eliminating the constant route fluctuations that cause intermittent connectivity.

Why the other options are wrong:

• A. Reducing OSPF AD is irrelevant; OSPF is not shown in this topology and the redistribution is between EIGRP and BGP only.
• C. Removing BGP and using another protocol would require significant network redesign and doesn't address the root cause of the mutual redistribution loop that needs to be managed via AD adjustment.
• D. R3 and R4 are already using eBGP (different AS), so this doesn't apply; the issue is route preference instability at R3, not the BGP session type.

Correct answer: C

The Required Min RX Interval is the minimum time spacing that must be observed between BFD control packets. This parameter defines the minimum interval at which a system can receive BFD packets and is used to determine the detection time for link failures. When a control packet arrives, the next packet must not arrive sooner than the Required Min RX Interval to avoid overwhelming the receiver.

Why the other options are wrong:

• A. Desired Min TX Interval specifies how often the system wants to send packets, not the minimum spacing for receiving them.
• B. Detect Mult is a multiplier used to calculate the detection time (Detect Mult × advertised interval), not a minimum time spacing between received packets.
• D. Required Min Echo RX Interval applies to the echo function of BFD, not to regular control packet reception.

Correct answer: B

The 'set ip default next-hop' command is used in route policy or policy routing to forward packets to a specified interface when the destination address is not found in the routing table. This is the standard command for handling packets destined to unknown networks by sending them to a default next hop.

Why the other options are wrong:

• A. The 'set ip next-hop' command sets a next hop for specific routes, not for all unmatched destinations.
• C. The 'set ip next-hop recursive' command performs recursive lookups on the next hop, not for default forwarding to unknown destinations.
• D. The 'set ip next-hop verify-availability' command verifies next-hop reachability but does not handle default forwarding for unmatched routes.

Correct answer: D

BFD (Bidirectional Forwarding Detection) provides sub-second failure detection for both Layer 1 (physical link) and Layer 2 (data link) problems. It operates at these lower layers to quickly identify link failures and trigger routing protocol updates. This sub-second detection is one of BFD's primary advantages over relying on routing protocol hello timers alone.

Why the other options are wrong:

• A. BFD does not directly update the routing table itself; it triggers routing protocols to update, and it detects layer 1/2 issues, not purely layer 1.
• B. BFD operates at layers 1 and 2, not layer 3, and it detects the failure to allow routing protocols to respond.
• C. BFD detects layer 1 and 2 problems, not layer 1 and 3 problems.

Correct answer: C

When OSPF neighbors are stuck in EXSTART/EXCHANGE state, it typically indicates a problem with Maximum Transmission Unit (MTU) mismatch. During the exchange of Database Description packets in these states, MTU mismatches cause packets to be dropped or rejected, preventing progression to FULL state. Matching MTU sizes between routers resolves this issue.

Why the other options are wrong:

• A. Password mismatches prevent adjacency from forming at all (routers stay in INIT or DOWN state), not causing EXSTART/EXCHANGE state.
• B. Hello timer mismatches prevent initial neighbor discovery but don't cause routers to get stuck in EXSTART/EXCHANGE state.
• D. Network type mismatches affect neighbor discovery and adjacency formation broadly, not specifically cause EXSTART/EXCHANGE state stalling.

Correct answer: C

The exhibit shows the interface GigabitEthernet0/0 transitioning between DOWN and UP states multiple times within milliseconds, indicating flapping. The log entries show %LINEPROTO-5-UPDOWN and %LINK-3-UPDOWN messages, which are characteristic of interface instability. IP Event Dampening (IED) is a feature that suppresses interfaces experiencing rapid state changes by keeping them administratively down after detecting excessive flapping. This prevents the interface from stabilizing, which explains why R2 cannot ping R1 despite the interface eventually coming up. Disabling or adjusting IP Event Dampening will allow the interface to stabilize properly.

Why the other options are wrong:

• A. Route dampening is a BGP feature that suppresses unstable routes, not a direct cause of interface flapping or connectivity issues between directly connected routers.
• B. While SFP compatibility issues could cause flapping, the log shows a pattern consistent with dampening rather than hardware incompatibility, and replacing hardware is premature without confirming this as the root cause.
• D. IP SLA probes measure network performance and wouldn't cause the interface state flapping pattern shown in the logs; this is an infrastructure monitoring tool, not a cause of connectivity failure.

Correct answer: A

Mutual redistribution between OSPF and EIGRP creates routing loops because routes redistributed from one protocol into the other can be redistributed back, causing instability. The solution is to tag routes when redistributing EIGRP into OSPF on R1, then match and deny those same tagged routes when redistributing OSPF back into EIGRP on R2. This prevents the EIGRP routes that were converted to OSPF routes from being redistributed back into EIGRP, breaking the redistribution loop while maintaining one-way flow of routing information.

Why the other options are wrong:

• B. Matching a tag to allow routes would still permit the looped routes back into EIGRP, perpetuating the instability rather than preventing it.
• C. Using a prefix list to propagate routes back into EIGRP would continue the loop and worsen network instability.
• D. Advertising summary routes does not prevent the fundamental problem of mutual redistribution loops; routes would still cycle between protocols.

Correct answer: A

When EIGRP is redistributed into OSPF on R3, the network 10.1.1.0/24 becomes an external OSPF route (Type 2 by default with metric 20). R4, which is in OSPF, now sees 10.1.1.0/24 via R3 with OSPF external metric. However, R4 also has a direct EIGRP path to 10.1.1.0/24 through R2. The problem is that R4 is taking a suboptimal path through R5 to reach 10.1.1.0/24. This occurs because the redistributed EIGRP route into OSPF has a low cost, making R4 prefer going through R5 and R3 rather than directly through R2. By increasing the administrative distance of external EIGRP routes to 90 (higher than the default EIGRP AD of 90 for internal routes, but this makes external redistributed routes less preferred), R4 will prefer its direct EIGRP path through R2, while R5 can still reach 10.1.1.0/24 via the OSPF external route from R3.

Why the other options are wrong:

• B. Applying an outbound distribution list on R5 toward R4 would prevent R5 from advertising the route, breaking reachability from R5 to 10.1.1.0/24.
• C. Changing OSPF AD to 200 on R5 would make OSPF routes unreliable and would not fix the suboptimal path issue for R4; it only affects R5's routing decisions.
• D. Redistributing OSPF into EIGRP on R4 would create routing loops and redundant advertisements without solving the suboptimal path problem, as the issue is metric- based preference.

Correct answer: B

The traceroute shows packets are being routed via R2 to R3 instead of the direct R1-R3 link, causing slowness. Looking at R1's routing table, there is a static route for 192.168.3.0/24 that points via 192.168.12.2 (R2) with a metric of [90/2681856]. This static route is overriding the direct dynamic route that would use the R1-R3 serial link. Since all serial links have equal bandwidth, the direct path R1→R3 would be superior to the indirect path R1→R2→R3. Removing the static route allows the dynamic routing protocol to select the better direct path, eliminating the performance issue.

Why the other options are wrong:

• A. Adding another static route to R3 would not remove the existing suboptimal static route; both routes would coexist and the routing decision would depend on metric comparison, not resolving the core problem of the existing poor route.

Correct answer: A

The engineer wants to set tag 30 to route 10.1.80.65/32, but the current configuration applies tag 30 to routes matching ccnp3 (10.1.64.0/24 le 24), which doesn't include 10.1.80.65/32. The route 10.1.80.65/32 actually matches ccnp2 (10.1.80.0/24 le 32), which currently has tag 20 assigned via permit 20. To assign tag 30 to 10.1.80.65/32, the route- map ospf-to-eigrp permit 10 must be modified to match prefix-list ccnp2 instead of ccnp1, and its tag should be changed to 30, or alternatively the permit 30 route-map should match ccnp2. Option A correctly identifies modifying permit 10 to match ccnp2 to capture this route with tag 30.

Why the other options are wrong:

• B. Adding 10.1.64.0/20 ge 32 to ccnp3 would match only /32 prefixes in that range, not 10.1.80.65/32 which is outside the 10.1.64.0/20 block.
• C. Modifying ccnp3 to add 10.1.64.0/20 le 24 doesn't help because 10.1.80.65/32 is not within the 10.1.64.0/20 range at all.
• D. Modifying permit 30 to match ccnp2 would change the tag assignment for ccnp2 routes from 20 to 10, creating incorrect tag assignments and contradicting the goal of assigning tag 30.

Correct answer: D

To resolve high route processor utilization caused by BGP packet drops, policing (not shaping) should be applied with the CIR (Committed Information Rate) to regulate BGP traffic. Both conform and exceed actions should transmit the packets to allow BGP to function while rate-limiting. This prevents the route processor from being overwhelmed while maintaining BGP adjacencies and route stability.

Why the other options are wrong:

• A. Shaping is used for traffic smoothing on output queues, not for control plane protection; PIR is wrong parameter, and the actions are incorrect.
• B. While policing is correct, using PIR instead of CIR is inappropriate for this scenario, and the actions (set-prec-transmit and set-clp-transmit) are incorrect.
• C. Shaping is inappropriate for control plane policing; CIR can be used with shaping but transmitting on both conform and exceed defeats the rate-limiting purpose.

Correct answer: B

BFD (Bidirectional Forwarding Detection) is the optimal mechanism to reduce OSPF reconvergence time with less CPU overhead than lowering hello and dead timers. BFD provides sub-second failure detection at lower protocol layers and notifies OSPF immediately when a link fails, allowing fast reconvergence without increasing the processing burden of frequent hello packet exchanges.

Why the other options are wrong:

• A. SSO (Stateful Switchover) is for router redundancy and does not optimize OSPF reconvergence time.
• C. Dead Peer Detection keepalives are used for BGP, not OSPF, and do not provide the same convergence benefits as BFD.
• D. OSPF demand circuit reduces LSA flooding but does not optimize reconvergence time for topology changes.

Correct answer: B

The debug output shows that BGP neighbor AB01:2011:7:100::3 is in 'Idle' state with 0 messages received and sent, indicating the neighbors are not exchanging BGP updates. The issue is that while the IPv6 neighbors are configured, the IPv6 address family is not activated for these neighbors. In BGP, after configuring a neighbor, you must explicitly activate it within the address-family ipv6 context for IPv6 routes to be exchanged. Option B configures R3 to activate the neighbor AB01:2011:7:100::1 within the IPv6 address family, which enables BGP to exchange IPv6 routes with R1. The corresponding activation on R1 would also be needed, but among the given options, B directly addresses the root cause of the adjacency problem.

Why the other options are wrong:

• A. While this activates the neighbor in IPv6 address family on R1, the question asks for the single configuration that resolves the issue, and R3 must also activate its neighbor for bidirectional route exchange to work.
• C. EBGP multihop is not needed here since the routers are directly connected via the E0/0 and E0/1 interfaces with adjacent IPv6 addresses.
• D. EBGP multihop on R3 does not address the actual problem; the neighbors cannot establish adjacency because the IPv6 address family is not activated, not because of hop count restrictions.

Correct answer: A

The debug output shows EIGRP HELLO packets being sent between R1 and R2, but no adjacency is being formed. The exhibit indicates both routers are in EIGRP AS 100, but the critical issue for EIGRP adjacency is that both routers must be configured with the same autonomous system number. Without matching AS numbers, routers will send HELLO packets but will not establish an adjacency relationship, which explains why the HELLO messages are being sent but the neighbors are not becoming adjacent. Configuring the same AS number on both routers is the fundamental requirement to form EIGRP adjacencies.

Why the other options are wrong:

• B. Hello interval mismatches don't prevent adjacency formation; routers can still become neighbors even with different hello intervals, though dead intervals need to be compatible.
• C. Authentication keys are optional in EIGRP; if not configured, routers can still form adjacencies without authentication enabled.
• D. EIGRP process IDs can differ between routers; they are local identifiers and do not affect adjacency formation between different routers.

Correct answer: B

The problem is a routing loop caused by mutual redistribution between BGP and EIGRP on R3, and between EIGRP and OSPF on R1. The 10.1.1.0/24 prefix originates in BGP AS64512 and gets redistributed into EIGRP on R3, then redistributed into OSPF on R1. This same prefix can be redistributed back from OSPF to EIGRP to BGP, creating a loop that causes frequent routing changes and instability. Tagging the prefix and denying it from being redistributed into OSPF on R1 breaks this loop by preventing the return path, stabilizing routing and eliminating the packet loss.

Why the other options are wrong:

• A. The issue is not OSPF SPF calculations or CPU on R3, but rather a routing loop caused by mutual redistribution; reducing SPF would not address the fundamental cause.
• C. Placing a distribute-list on R3 blocking the prefix from OSPF advertisement does not solve the problem since the loop is created by redistribution on R1, not advertisements from R3.
• D. Testing the link from R4 to the local prefix and checking Layer 2 errors is irrelevant; the R3 to R4 link was already tested with no packet loss, and the issue is a routing loop, not a physical layer problem.