Question 230 An upstream receives a BGP update containing its own AS in AS_PATH and the route is rejected. Which technical mechanism best explains the behavior observed in this scenario? BGP evaluates local preference before AS-path length when other earlier conditions are equal. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. ExplanationCorrect Answer B:BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. This explains why the initial condition produces the observed failure. The direct repair is: Find the policy or topology that reintroduced the upstream's AS rather than disabling the loop check as a routine fix. Validate through: Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. Other Answers A:BGP evaluates local preference before AS-path length when other earlier conditions are equal. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. C:BGP transport reachability does not by itself activate exchange for every multiprotocol address family. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. D:Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default.
Question 231 An upstream receives a BGP update containing its own AS in AS_PATH and the route is rejected. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Compare the full path attributes, then demonstrate the expected winner after removing the unintended override. Inspect neighboring AS values and compare the selected path under the approved MED policy. Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. Check BGP advertised-routes toward the missing client and the corresponding route-reflector state. ExplanationCorrect Answer C:Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. Other Answers A:Compare the full path attributes, then demonstrate the expected winner after removing the unintended override. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. B:Inspect neighboring AS values and compare the selected path under the approved MED policy. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. D:Check BGP advertised-routes toward the missing client and the corresponding route-reflector state. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default.
Question 232 An upstream receives a BGP update containing its own AS in AS_PATH and the route is rejected. Which lasting design or operational safeguard best prevents this particular issue from recurring? Coordinate traffic engineering with upstream routing policy and verify real path impact. Document whether traffic-engineering policy is local-only or AS-wide before choosing attributes. Maintain explicit route-reflector topology and client inventory. Review AS-path manipulation and peering topology whenever routes traverse multiple boundaries. ExplanationCorrect Answer D:Review AS-path manipulation and peering topology whenever routes traverse multiple boundaries. This addresses the recurring cause: BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. A targeted acceptance check is: Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. Other Answers A:Coordinate traffic engineering with upstream routing policy and verify real path impact. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. B:Document whether traffic-engineering policy is local-only or AS-wide before choosing attributes. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. C:Maintain explicit route-reflector topology and client inventory. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default.
Question 233 A new peer is Established but only IPv4 prefixes arrive; the operator enabled IPv6 addressing on the interface without activating the IPv6 unicast address family. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. Use an AS-propagated attribute such as local preference instead of relying on router-local weight. Validate AS-path prepending from external peers and treat it as a remote-inbound influence rather than a guaranteed local choice. Introduce the approved route-reflector client relationship or build required full-mesh sessions. ExplanationCorrect Answer A:Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Other Answers B:Use an AS-propagated attribute such as local preference instead of relying on router-local weight. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. C:Validate AS-path prepending from external peers and treat it as a remote-inbound influence rather than a guaranteed local choice. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. D:Introduce the approved route-reflector client relationship or build required full-mesh sessions. BGP transport reachability does not by itself activate exchange for every multiprotocol address family.
Question 234 A new peer is Established but only IPv4 prefixes arrive; the operator enabled IPv6 addressing on the interface without activating the IPv6 unicast address family. Which technical mechanism best explains the behavior observed in this scenario? A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. BGP evaluates local preference before AS-path length when other earlier conditions are equal. ExplanationCorrect Answer B:BGP transport reachability does not by itself activate exchange for every multiprotocol address family. This explains why the initial condition produces the observed failure. The direct repair is: Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. Validate through: Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Other Answers A:A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. C:Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. D:BGP evaluates local preference before AS-path length when other earlier conditions are equal. BGP transport reachability does not by itself activate exchange for every multiprotocol address family.
Question 235 A new peer is Established but only IPv4 prefixes arrive; the operator enabled IPv6 addressing on the interface without activating the IPv6 unicast address family. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Compare best paths on the configured router and a different iBGP router after changing local preference. Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Inspect next-hop reachability and confirm a formerly inaccessible BGP prefix becomes valid and installed. ExplanationCorrect Answer C:Show IPv6 unicast neighbor activation and the expected prefixes on both peers. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: BGP transport reachability does not by itself activate exchange for every multiprotocol address family. Other Answers A:Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. B:Compare best paths on the configured router and a different iBGP router after changing local preference. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. D:Inspect next-hop reachability and confirm a formerly inaccessible BGP prefix becomes valid and installed. BGP transport reachability does not by itself activate exchange for every multiprotocol address family.
Question 236 A new peer is Established but only IPv4 prefixes arrive; the operator enabled IPv6 addressing on the interface without activating the IPv6 unicast address family. Which lasting design or operational safeguard best prevents this particular issue from recurring? Review attribute precedence whenever inbound path-manipulation route-maps change. Regression-test reflection and filtering for every client when modifying cluster policy. Coordinate traffic engineering with upstream routing policy and verify real path impact. Use per-AF activation and route-policy checklists for MP-BGP sessions. ExplanationCorrect Answer D:Use per-AF activation and route-policy checklists for MP-BGP sessions. This addresses the recurring cause: BGP transport reachability does not by itself activate exchange for every multiprotocol address family. A targeted acceptance check is: Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Other Answers A:Review attribute precedence whenever inbound path-manipulation route-maps change. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. B:Regression-test reflection and filtering for every client when modifying cluster policy. BGP transport reachability does not by itself activate exchange for every multiprotocol address family. C:Coordinate traffic engineering with upstream routing policy and verify real path impact. BGP transport reachability does not by itself activate exchange for every multiprotocol address family.
Question 237 An inbound BGP prefix list was updated, but old accepted prefixes remain until the operator performs a full neighbor reset. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Use supported inbound route refresh or soft policy re-evaluation before disruptive hard resets. Set the intended local preference consistently for the preferred egress route. Set the correct loopback `update-source` and peer address consistently on both ends. Find the policy or topology that reintroduced the upstream's AS rather than disabling the loop check as a routine fix. ExplanationCorrect Answer A:Use supported inbound route refresh or soft policy re-evaluation before disruptive hard resets. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. Verify policy changes take effect while neighbor Established uptime remains continuous. Other Answers B:Set the intended local preference consistently for the preferred egress route. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. C:Set the correct loopback `update-source` and peer address consistently on both ends. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. D:Find the policy or topology that reintroduced the upstream's AS rather than disabling the loop check as a routine fix. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering.
Question 238 An inbound BGP prefix list was updated, but old accepted prefixes remain until the operator performs a full neighbor reset. Which technical mechanism best explains the behavior observed in this scenario? BGP transport reachability does not by itself activate exchange for every multiprotocol address family. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. Cisco weight affects only the local BGP decision and is not advertised to other routers. ExplanationCorrect Answer B:BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. This explains why the initial condition produces the observed failure. The direct repair is: Use supported inbound route refresh or soft policy re-evaluation before disruptive hard resets. Validate through: Verify policy changes take effect while neighbor Established uptime remains continuous. Other Answers A:BGP transport reachability does not by itself activate exchange for every multiprotocol address family. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. C:Cisco BGP ordinarily compares MED only among paths received from the same neighboring AS, subject to configuration exceptions. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. D:Cisco weight affects only the local BGP decision and is not advertised to other routers. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering.
Question 239 An inbound BGP prefix list was updated, but old accepted prefixes remain until the operator performs a full neighbor reset. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Check BGP advertised-routes toward the missing client and the corresponding route-reflector state. Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Verify policy changes take effect while neighbor Established uptime remains continuous. Check local-pref values and the selected best path on internal BGP speakers. ExplanationCorrect Answer C:Verify policy changes take effect while neighbor Established uptime remains continuous. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. Other Answers A:Check BGP advertised-routes toward the missing client and the corresponding route-reflector state. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. B:Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. D:Check local-pref values and the selected best path on internal BGP speakers. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering.
Question 240 An inbound BGP prefix list was updated, but old accepted prefixes remain until the operator performs a full neighbor reset. Which lasting design or operational safeguard best prevents this particular issue from recurring? Centralize egress local-preference policy and test best-path order when adding peers. Include underlay reachability, TTL and update-source in loopback-peering templates. Review attribute precedence whenever inbound path-manipulation route-maps change. Plan nondisruptive BGP policy refresh procedures for routine filters. ExplanationCorrect Answer D:Plan nondisruptive BGP policy refresh procedures for routine filters. This addresses the recurring cause: BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. A targeted acceptance check is: Verify policy changes take effect while neighbor Established uptime remains continuous. Other Answers A:Centralize egress local-preference policy and test best-path order when adding peers. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. B:Include underlay reachability, TTL and update-source in loopback-peering templates. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering. C:Review attribute precedence whenever inbound path-manipulation route-maps change. BGP route refresh lets a speaker reapply an inbound policy to received updates without tearing down TCP peering.
