Cisco 350-501 Practice Test 22
Question 210
For an original SPCOR service-provider engineering scenario, consider: Two transit paths carry the same prefix and the operator wants all egress to prefer one upstream but modifies MED on an unrelated inbound route. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements.
- Check: Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Change: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
- Check: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- Assume shortest AS_PATH always wins regardless of higher-priority local preference or invalid route candidates.
Explanation
Correct Answer
B:Acceptance: The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. Applied case: Two transit paths carry the same prefix and the operator wants all egress to prefer one upstream but modifies MED on an unrelated inbound route.
C:Acceptance: The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Incorrect Answers
A:Change: Troubleshoot OSPF network type, area, neighbor timers, authentication and database-exchange parameters before modifying routing advertisements. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
D:Check: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
E:BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context. Use this instead: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
Question 211
A service provider network engineer is reviewing this backbone or customer-service scenario: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria. A proposed shortcut is: Assume shortest AS_PATH always wins regardless of higher-priority local preference or invalid route candidates. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction.
- Assume shortest AS_PATH always wins regardless of higher-priority local preference or invalid route candidates.
- Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
- Choose the appropriate IPv6 transition and address-sharing model for subscriber connectivity, and test mapping state and application behavior end to end.
Explanation
Correct Answer
C:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
Incorrect Answers
A:Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction. A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
B:BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context. Applied case: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
D:This option addresses a different service provider engineering topic (NAT64 CGNAT MAP-T DS-Lite and transition selection) rather than the documented BGP path selection weight local preference and AS path decision.
Question 212
A Cisco service provider design review finds: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria. The team proposes: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
- LACP negotiates compatible members into a logical bundle while per-flow hashing commonly keeps a flow on one member to preserve packet order.
- BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
- BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Explanation
Correct Answer
D:Demonstrable success requires: The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. Applied case: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
Incorrect Answers
A:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
B:LACP negotiates compatible members into a logical bundle while per-flow hashing commonly keeps a flow on one member to preserve packet order. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
C:This option addresses a different service provider engineering topic (eBGP IPv4 IPv6 peer and multihop session design) rather than the documented BGP path selection weight local preference and AS path decision.
Question 213
The service provider operations team has not yet approved a change. Current evidence indicates: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers.
- Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Compare per-protocol neighbor state, error messages, encapsulation, path reachability, authentication and interface counters.
- Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram.
Explanation
Correct Answer
B:Confirm afterward that: The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. Applied case: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria.
Incorrect Answers
A:Check neighbor state transitions, interface MTU, hello and dead intervals, area type and network type on both peers. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
C:Compare per-protocol neighbor state, error messages, encapsulation, path reachability, authentication and interface counters. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
D:Examine NET values, level adjacency state, LSP originator IDs and intended area boundaries on a two-area diagram. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Question 214
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria. The carrier operations owner needs positive and negative tests showing existing customer services remain available. Which acceptance result demonstrates correct service provider forwarding and control behavior without disrupting authorized workflows? Select ONE best answer.
- Authorized prefixes are imported or exported and unintended customer or infrastructure prefixes are rejected without adjacency disruption.
- Clients receive intended routes without reflection loops and installed paths resolve to reachable transport next hops.
- The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
- Preferred paths align with declared metrics while all participating routers interpret the advertised costs consistently.
Explanation
Correct Answer
C:BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Authorized prefixes are imported or exported and unintended customer or infrastructure prefixes are rejected without adjacency disruption. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
B:Clients receive intended routes without reflection loops and installed paths resolve to reachable transport next hops. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
D:Preferred paths align with declared metrics while all participating routers interpret the advertised costs consistently. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Question 215
An implementation sign-off request identifies the following problem: A provider receives two routes with different LOCAL_PREF values yet diagnoses the choice solely from AS_PATH length despite earlier selection criteria. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Verify aggregation protocol, member compatibility, hashing expectations and actual active bandwidth before designing redundancy or QoS. Verify: Inspect member actor and partner state, bundle hashing, counters and traffic distribution under several representative flows.
- Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy. Verify: Review link metric TLVs, enabled metric style, SPF database and before-after path selection for two candidate routes.
- Change: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. Verify: Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Change: Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure. Verify: Measure neighbor resets, stale route retention, forwarding counters and route processing after a planned RP switchover.
Explanation
Correct Answer
C:The change is successful only when: The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
Incorrect Answers
A:Change: Verify aggregation protocol, member compatibility, hashing expectations and actual active bandwidth before designing redundancy or QoS. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
B:Change: Apply supported consistent metric style and tune link costs to the provider's intended shortest-path and capacity policy. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
D:Change: Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure. BGP best-path selection considers local policy such as weight and local preference before several later tie breakers, including path length and MED context.
Question 216
A service provider network engineer is reviewing this backbone or customer-service scenario: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic. A proposed shortcut is: Send arbitrary community numbers with no matching import policy and treat them as automatic global routing commands. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction.
- Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation.
- Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures.
- Send arbitrary community numbers with no matching import policy and treat them as automatic global routing commands.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic.
Incorrect Answers
A:Use the platform's supported policy language, explicit prefix sets and match sequencing to permit only intended routes and apply actions at the correct direction. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
C:Tune consistent OSPF cost or reference-bandwidth settings and validate reconvergence under controlled link failures. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
D:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
Question 217
A Cisco service provider design review finds: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic. The team proposes: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
- Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems.
- IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability.
- Redistribution changes protocol scope and metrics; uncontrolled mutual redistribution can create loops and excessive IGP state.
Explanation
Correct Answer
A:Demonstrable success requires: Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect. Applied case: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic.
Incorrect Answers
B:Graceful restart can retain forwarding with peer help during control recovery, while NSR replicates live session state on supported dual-control-plane systems. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
C:IS-IS NET encodes an area and unique system identifier; Level-1 flooding is area scoped while Level-2 connects interarea backbone reachability. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
D:Redistribution changes protocol scope and metrics; uncontrolled mutual redistribution can create loops and excessive IGP state. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
Question 218
The service provider operations team has not yet approved a change. Current evidence indicates: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- Inspect BGP neighbor transport state, local and remote AS, update source, TCP reachability and IPv4 or IPv6 address-family activation.
- Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie.
- Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family.
Explanation
Correct Answer
A:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. Applied case: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic.
Incorrect Answers
B:Inspect BGP neighbor transport state, local and remote AS, update source, TCP reachability and IPv4 or IPv6 address-family activation. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
C:Compare valid path candidates and detailed BGP attributes under a test prefix, then trace which decision criterion breaks the tie. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
D:Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
Question 219
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic. The carrier operations owner needs positive and negative tests showing existing customer services remain available. Which acceptance result demonstrates correct service provider forwarding and control behavior without disrupting authorized workflows? Select ONE best answer.
- Each intended adjacency reaches its required state and route advertisements are scoped correctly without unnecessary global routing changes.
- Both address families receive valid advertised next hops for the chosen topology mode and failures are diagnosed per family.
- Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect.
- Unique node identities produce the intended L1 or L2 adjacencies and routes cross only supported level boundaries.
Explanation
Correct Answer
C:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Each intended adjacency reaches its required state and route advertisements are scoped correctly without unnecessary global routing changes. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
B:Both address families receive valid advertised next hops for the chosen topology mode and failures are diagnosed per family. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
D:Unique node identities produce the intended L1 or L2 adjacencies and routes cross only supported level boundaries. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
Question 220
For an original SPCOR service-provider engineering scenario, consider: A customer tags prefixes with a provider-defined blackhole community but the transit AS has no explicit matching policy and does not discard traffic. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Check: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- Send arbitrary community numbers with no matching import policy and treat them as automatic global routing commands.
- Change: Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls.
- Check: Inspect negotiated additional-path capability, backup path RIB and FIB entries and forwarding interruption during simulated failure.
- Change: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation.
Explanation
Correct Answer
A:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. Acceptance: Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect.
E:BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction. Evidence: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
Incorrect Answers
B:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
C:Change: Diagnose the affected protocol's actual session prerequisites and advertisement scope before changing unrelated routing controls. BGP communities carry policy tags whose meaning depends on configured policy; local preference influences internal outbound selection but is not a universal external traffic-engineering instruction.
D:This option addresses a different service provider engineering topic (BGP Additional Paths PIC and fast failover) rather than the documented BGP route-policy communities and provider preference decision.
