Cisco 350-501 Practice Test 23
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.
Question 221
A service provider network engineer is reviewing this backbone or customer-service scenario: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference. 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.
- Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary.
- Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation.
- Send arbitrary community numbers with no matching import policy and treat them as automatic global routing commands.
- Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives.
Explanation
Correct Answer
B:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference.
Incorrect Answers
A:Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. 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: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 carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference.
D:Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives. 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 222
A Cisco service provider design review finds: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference. 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.
- MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
- IS-IS adjacencies use link-local protocol hellos and compatible level, circuit and network settings; IP reachability alone does not create a neighbor.
- OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance.
- 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.
Explanation
Correct Answer
D:Demonstrable success requires: Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect. Applied case: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference.
Incorrect Answers
A:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. 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:This option addresses a different service provider engineering topic (IS-IS neighbor adjacency and link readiness) rather than the documented BGP route-policy communities and provider preference decision.
C:OSPF SPF evaluates cumulative link costs, including configured interface cost and supported reference-bandwidth scaling, not geographic distance. 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 223
The service provider operations team has not yet approved a change. Current evidence indicates: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes.
- Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests.
- Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
- Compare BFD session state, negotiated intervals, packet drops and routing convergence after controlled loss and benign congestion tests.
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. Confirm afterward that: Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect.
Incorrect Answers
A:Inspect IPv6 link-local neighbors, interface instance and area data, OSPFv3 LSDB and installed IPv6 routes. 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:Record each link cost and LSDB view, calculate expected shortest paths and compare route changes during shut and no-shut tests. 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 BFD session state, negotiated intervals, packet drops and routing convergence after controlled loss and benign congestion tests. 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 224
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference. 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.
- Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets.
- Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers.
- Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect.
- Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling.
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 approved implementation step was: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation.
Incorrect Answers
A:Genuine path loss is detected promptly while minor delay variation does not trigger avoidable adjacency resets. 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:Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers. 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:Authorized IPv6 and shared-IPv4 applications work with correct port mappings, accountability and predictable failure handling. A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference.
Question 225
An implementation sign-off request identifies the following problem: A carrier wants to reduce inbound advertisements to one upstream yet changes LOCAL_PREF internally and assumes external neighbors will see that preference. Which paired technical change and validation should close the implementation review? Select ONE best answer.
- Change: Deploy route reflection with deliberate client and cluster design and preserve IGP reachability to advertised BGP next hops. Verify: Check route-reflector client relationships, originator and cluster attributes, BGP next-hop resolution and the RIB versus FIB.
- Change: 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. Verify: Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence.
- 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: Apply documented BGP community or extended-community policies at the intended import or export point and verify resulting attribute propagation. Verify: Check received and advertised BGP attributes, applied route policy, peer documentation and resulting best path for a controlled test prefix.
Explanation
Correct Answer
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. The change is successful only when: Only policy-matched routes change forwarding or advertisement behavior and customer communities have their documented effect.
Incorrect Answers
A:This option addresses a different service provider engineering topic (iBGP route reflector cluster and next-hop reachability) rather than the documented BGP route-policy communities and provider preference decision.
B:Change: 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.
C:Change: Evaluate the ordered BGP decision process and set the intended local policy attribute at the correct AS boundary. 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 226
A service provider network engineer is reviewing this backbone or customer-service scenario: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system. A proposed shortcut is: Guarantee every independent internet AS will honor one MED or prepend irrespective of its own routing policy. What should the service provider engineer recommend as the narrowly scoped correction? Select ONE best answer.
- Guarantee every independent internet AS will honor one MED or prepend irrespective of its own routing policy.
- Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure.
- Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives.
- Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas.
Explanation
Correct Answer
C:This targeted action addresses the observed service-provider control or forwarding gap without discarding necessary controls. Applied case: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system.
Incorrect Answers
A:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. For this best change assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it.
B:Configure high availability features with supported peer behavior and validate which control and forwarding states are preserved during process or RP failure. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
D:Assign unique IS-IS system IDs and consistent area identifiers for Level-1 adjacency, with proper Level-2 reachability across areas. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
Question 227
A Cisco service provider design review finds: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system. The team proposes: Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives. Which engineering principle most strongly supports the recommended response? Select ONE best answer.
- MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
- BFD detects data-path forwarding failure independently of slower routing hellos but extreme timer settings can create false failures.
- iBGP does not ordinarily re-advertise routes learned from one iBGP peer to another without route reflection or confederations; next-hop validation remains required.
- BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions.
Explanation
Correct Answer
A:Demonstrable success requires: Steering influences targeted peers as expected while reachability is preserved when remote policy ignores the hint. Applied case: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system.
Incorrect Answers
B:BFD detects data-path forwarding failure independently of slower routing hellos but extreme timer settings can create false failures. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
C:IBGP does not ordinarily re-advertise routes learned from one iBGP peer to another without route reflection or confederations; next-hop validation remains required. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
D:BGP TCP sessions depend on correct peer identity and routed transport; external versus internal peer behavior changes next-hop and forwarding assumptions. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
Question 228
The service provider operations team has not yet approved a change. Current evidence indicates: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system. Which evidence best tests the technical diagnosis before approving a disruptive change? Select ONE best answer.
- Examine advertised route attributes per peer, remote looking-glass paths and measured ingress flows before and after the change.
- Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses.
- Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence.
- Check route-reflector client relationships, originator and cluster attributes, BGP next-hop resolution and the RIB versus FIB.
Explanation
Correct Answer
A:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. Applied case: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system.
Incorrect Answers
B:Compare area LSDB LSA types, ABR summaries, default injection and actual endpoint reachability for inside and outside addresses. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
C:Evaluate a test table with allowed, denied and boundary prefixes against actual show-policy and BGP advertised-routes evidence. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
D:Check route-reflector client relationships, originator and cluster attributes, BGP next-hop resolution and the RIB versus FIB. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
Question 229
A candidate correction has been tested and the platform team requires a post-change acceptance check. Original problem: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system. 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.
- Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers.
- Steering influences targeted peers as expected while reachability is preserved when remote policy ignores the hint.
- The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure.
- Intended EBGP adjacencies establish securely and exchange only approved prefixes in the selected address family.
Explanation
Correct Answer
B:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. The result must be validated using the documented device, service or access context.
Incorrect Answers
A:Failure recovery stays within service limits and no stale unvalidated forwarding state persists beyond documented timers. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
C:The preferred transit path wins for documented policy reasons without unexpected route filtering or next-hop failure. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
D:Intended EBGP adjacencies establish securely and exchange only approved prefixes in the selected address family. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
Question 230
For an original SPCOR service-provider engineering scenario, consider: A multihomed provider wants remote traffic to prefer a particular link but assumes adding MED to one route controls every third-party autonomous system. Select TWO complementary steps: the targeted correction and its strongest prechange validation.
- Change: Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives.
- Guarantee every independent internet AS will honor one MED or prepend irrespective of its own routing policy.
- Check: Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family.
- Check: Examine advertised route attributes per peer, remote looking-glass paths and measured ingress flows before and after the change.
- Change: Enable compatible path diversity or BGP PIC mechanisms where supported and verify backup data-plane programming before a failure.
Explanation
Correct Answer
A:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. Acceptance: Steering influences targeted peers as expected while reachability is preserved when remote policy ignores the hint.
D:MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences. Required intervention: Choose documented BGP ingress-traffic engineering signals and verify how relevant peers actually compare received alternatives.
Incorrect Answers
B:For this select two assessment, the shortcut changes or bypasses the necessary routing, service or operational boundary rather than correcting it. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
C:Check: Compare IS-IS IPv4 and IPv6 LSP TLVs, topology IDs, next-hop tables and controlled ping tests for each family. MED influences comparisons under specific BGP decision contexts, and AS_PATH prepending is advisory because remote networks may apply their own preferences.
E:This option addresses a different service provider engineering topic (BGP Additional Paths PIC and fast failover) rather than the documented BGP MED AS_PATH prepending and ingress steering decision.
