Question 460 Loose uRPF allows a packet because a broad default route exists, even though the network team expects to block a forged source. Which lasting design or operational safeguard best prevents this particular issue from recurring? Validate supported syntax and feature matrices before distributing common ACL templates. Choose ACL type and placement according to the fields required by the security decision. Maintain end-to-end access path diagrams and test overlapping controls together. Use defined source-address allowlists and do not assume loose uRPF equals strict ingress validation. ExplanationCorrect Answer D:Use defined source-address allowlists and do not assume loose uRPF equals strict ingress validation. This addresses the recurring cause: Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings. A targeted acceptance check is: Send controlled spoofed-source test packets and verify the explicit source filter blocks them. Other Answers A:Validate supported syntax and feature matrices before distributing common ACL templates. Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings. B:Choose ACL type and placement according to the fields required by the security decision. Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings. C:Maintain end-to-end access path diagrams and test overlapping controls together. Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings.
Question 461 A border interface's source-validation policy starts dropping a newly routed customer prefix after the customer's legitimate routes are withdrawn. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Repair authorized reverse-route visibility and then verify uRPF before disabling spoofing protections globally. Verify the actual traffic ingress path and apply the policy to the correct interface and direction. Move the specific permit ahead of the matching deny while keeping the rest of the ACL's policy intact. Use an appropriately placed extended ACL that matches source, destination and required transport ports. ExplanationCorrect Answer A:Repair authorized reverse-route visibility and then verify uRPF before disabling spoofing protections globally. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. Inspect source RIB entry, interface uRPF counters and accepted customer packets after route recovery. Other Answers B:Verify the actual traffic ingress path and apply the policy to the correct interface and direction. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. C:Move the specific permit ahead of the matching deny while keeping the rest of the ACL's policy intact. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. D:Use an appropriately placed extended ACL that matches source, destination and required transport ports. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks.
Question 462 A border interface's source-validation policy starts dropping a newly routed customer prefix after the customer's legitimate routes are withdrawn. Which technical mechanism best explains the behavior observed in this scenario? Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings. uRPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. Cisco ACL entries are evaluated in order and processing stops at the first match. Time-range ACL evaluation depends on the router's effective time settings as well as packet matching. ExplanationCorrect Answer B:uRPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. This explains why the initial condition produces the observed failure. The direct repair is: Repair authorized reverse-route visibility and then verify uRPF before disabling spoofing protections globally. Validate through: Inspect source RIB entry, interface uRPF counters and accepted customer packets after route recovery. Other Answers A:Loose uRPF checks that a route to the source exists; a default route may satisfy that criterion depending on implementation settings. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. C:Cisco ACL entries are evaluated in order and processing stops at the first match. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. D:Time-range ACL evaluation depends on the router's effective time settings as well as packet matching. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks.
Question 463 A border interface's source-validation policy starts dropping a newly routed customer prefix after the customer's legitimate routes are withdrawn. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Use packet-path tracing and ACE counters to show the target flow actually encounters the policy. Inspect running policy and counters for representative new addresses after deployment. Inspect source RIB entry, interface uRPF counters and accepted customer packets after route recovery. Send controlled spoofed-source test packets and verify the explicit source filter blocks them. ExplanationCorrect Answer C:Inspect source RIB entry, interface uRPF counters and accepted customer packets after route recovery. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: uRPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. Other Answers A:Use packet-path tracing and ACE counters to show the target flow actually encounters the policy. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. B:Inspect running policy and counters for representative new addresses after deployment. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. D:Send controlled spoofed-source test packets and verify the explicit source filter blocks them. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks.
Question 464 A border interface's source-validation policy starts dropping a newly routed customer prefix after the customer's legitimate routes are withdrawn. Which lasting design or operational safeguard best prevents this particular issue from recurring? Use defined source-address allowlists and do not assume loose uRPF equals strict ingress validation. Validate supported syntax and feature matrices before distributing common ACL templates. Track required applications and implicit-deny cases in ACL policy matrices. Monitor source-prefix reachability alongside ingress anti-spoofing drops. ExplanationCorrect Answer D:Monitor source-prefix reachability alongside ingress anti-spoofing drops. This addresses the recurring cause: uRPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. A targeted acceptance check is: Inspect source RIB entry, interface uRPF counters and accepted customer packets after route recovery. Other Answers A:Use defined source-address allowlists and do not assume loose uRPF equals strict ingress validation. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. B:Validate supported syntax and feature matrices before distributing common ACL templates. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. C:Track required applications and implicit-deny cases in ACL policy matrices. URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks.
Question 465 An ACL references a named object group updated with new address entries, but a platform variant does not support the expected object-group syntax. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Verify feature support and compile an equivalent explicit supported ACE policy for the device release. Move the specific permit ahead of the matching deny while keeping the rest of the ACL's policy intact. Add a narrowly scoped permit for the authorized DNS traffic before the implicit deny. Correct and synchronize device time and validate the referenced time-range configuration. ExplanationCorrect Answer A:Verify feature support and compile an equivalent explicit supported ACE policy for the device release. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. Inspect running policy and counters for representative new addresses after deployment. Other Answers B:Move the specific permit ahead of the matching deny while keeping the rest of the ACL's policy intact. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. C:Add a narrowly scoped permit for the authorized DNS traffic before the implicit deny. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. D:Correct and synchronize device time and validate the referenced time-range configuration. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches.
Question 466 An ACL references a named object group updated with new address entries, but a platform variant does not support the expected object-group syntax. Which technical mechanism best explains the behavior observed in this scenario? Interface ACLs inspect packets only as they cross the configured interface in the specified direction. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. Time-range ACL evaluation depends on the router's effective time settings as well as packet matching. uRPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. ExplanationCorrect Answer B:ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. This explains why the initial condition produces the observed failure. The direct repair is: Verify feature support and compile an equivalent explicit supported ACE policy for the device release. Validate through: Inspect running policy and counters for representative new addresses after deployment. Other Answers A:Interface ACLs inspect packets only as they cross the configured interface in the specified direction. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. C:Time-range ACL evaluation depends on the router's effective time settings as well as packet matching. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. D:URPF depends on source-route lookup; losing a legitimate source route can make valid traffic fail reverse-path checks. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches.
Question 467 An ACL references a named object group updated with new address entries, but a platform variant does not support the expected object-group syntax. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Inspect ACE hit counts and verify only the intended DNS exchange now passes. Observe a permitted local ACL hit alongside a deny hit at the actual blocking policy. Inspect running policy and counters for representative new addresses after deployment. Use packet-path tracing and ACE counters to show the target flow actually encounters the policy. ExplanationCorrect Answer C:Inspect running policy and counters for representative new addresses after deployment. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. Other Answers A:Inspect ACE hit counts and verify only the intended DNS exchange now passes. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. B:Observe a permitted local ACL hit alongside a deny hit at the actual blocking policy. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. D:Use packet-path tracing and ACE counters to show the target flow actually encounters the policy. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches.
Question 468 An ACL references a named object group updated with new address entries, but a platform variant does not support the expected object-group syntax. Which lasting design or operational safeguard best prevents this particular issue from recurring? Monitor source-prefix reachability alongside ingress anti-spoofing drops. Include time synchronization monitoring for all time-dependent firewall and ACL policies. Track required applications and implicit-deny cases in ACL policy matrices. Validate supported syntax and feature matrices before distributing common ACL templates. ExplanationCorrect Answer D:Validate supported syntax and feature matrices before distributing common ACL templates. This addresses the recurring cause: ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. A targeted acceptance check is: Inspect running policy and counters for representative new addresses after deployment. Other Answers A:Monitor source-prefix reachability alongside ingress anti-spoofing drops. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. B:Include time synchronization monitoring for all time-dependent firewall and ACL policies. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches. C:Track required applications and implicit-deny cases in ACL policy matrices. ACL object-group support and expansion depend on platform and software; unsupported constructs do not create intended matches.
Question 469 BGP flaps during a burst of management traffic while hardware forwarding is healthy; a CoPP class policing all control traffic at one low rate is dropping BGP packets. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Separate critical routing protocols into correctly classified control-plane classes with justified policing rates. Check that the service-policy is actually applied in the supported control-plane direction. Move data-plane rate controls to the appropriate interface QoS mechanism instead of treating CoPP as transit QoS. Add correct IPv6 control-plane classification and rates for the intended BGP peers. ExplanationCorrect Answer A:Separate critical routing protocols into correctly classified control-plane classes with justified policing rates. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. Inspect CoPP class drop counters correlated with BGP session resets under controlled load. Other Answers B:Check that the service-policy is actually applied in the supported control-plane direction. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. C:Move data-plane rate controls to the appropriate interface QoS mechanism instead of treating CoPP as transit QoS. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. D:Add correct IPv6 control-plane classification and rates for the intended BGP peers. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic.
Question 470 BGP flaps during a burst of management traffic while hardware forwarding is healthy; a CoPP class policing all control traffic at one low rate is dropping BGP packets. Which technical mechanism best explains the behavior observed in this scenario? Unrestricted broad CoPP rate increases can remove protection of the router CPU while masking a classifier error. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. IPv4-only classifier syntax may not cover IPv6 packets even when the application protocol is the same. A CoPP class not matching SNMP can force it into default policing even when transport reachability and credentials are valid. ExplanationCorrect Answer B:CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. This explains why the initial condition produces the observed failure. The direct repair is: Separate critical routing protocols into correctly classified control-plane classes with justified policing rates. Validate through: Inspect CoPP class drop counters correlated with BGP session resets under controlled load. Other Answers A:Unrestricted broad CoPP rate increases can remove protection of the router CPU while masking a classifier error. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. C:IPv4-only classifier syntax may not cover IPv6 packets even when the application protocol is the same. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic. D:A CoPP class not matching SNMP can force it into default policing even when transport reachability and credentials are valid. CoPP can limit packets punted to the CPU; an overbroad class can starve essential routing control traffic.
