Question 220 A route reflector receives two paths from clients but one downstream client lacks a necessary route after reflection policy changes. Which lasting design or operational safeguard best prevents this particular issue from recurring? Use per-AF activation and route-policy checklists for MP-BGP sessions. Include end-to-end BGP next-hop reachability tests during iBGP rollouts. Use MED only where its comparison scope and inbound path attributes are intentionally defined. Regression-test reflection and filtering for every client when modifying cluster policy. ExplanationCorrect Answer D:Regression-test reflection and filtering for every client when modifying cluster policy. This addresses the recurring cause: A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. A targeted acceptance check is: Check BGP advertised-routes toward the missing client and the corresponding route-reflector state. Other Answers A:Use per-AF activation and route-policy checklists for MP-BGP sessions. A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. B:Include end-to-end BGP next-hop reachability tests during iBGP rollouts. A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. C:Use MED only where its comparison scope and inbound path attributes are intentionally defined. A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection.
Question 221 Two eBGP loopback-sourced peers cannot establish a session because default single-hop TTL cannot reach the distant loopbacks. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Use the supported eBGP multihop design plus correct update-source and routable peer loopbacks. Introduce the approved route-reflector client relationship or build required full-mesh sessions. Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. Correct the overriding policy before assuming AS-path length will select the path. ExplanationCorrect Answer A:Use the supported eBGP multihop design plus correct update-source and routable peer loopbacks. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Other Answers B:Introduce the approved route-reflector client relationship or build required full-mesh sessions. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. C:Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. D:Correct the overriding policy before assuming AS-path length will select the path. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption.
Question 222 Two eBGP loopback-sourced peers cannot establish a session because default single-hop TTL cannot reach the distant loopbacks. Which technical mechanism best explains the behavior observed in this scenario? BGP next-hop resolution is a prerequisite for installing an otherwise valid received path into the RIB. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. Cisco weight affects only the local BGP decision and is not advertised to other routers. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. ExplanationCorrect Answer B:Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. This explains why the initial condition produces the observed failure. The direct repair is: Use the supported eBGP multihop design plus correct update-source and routable peer loopbacks. Validate through: Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Other Answers A:BGP next-hop resolution is a prerequisite for installing an otherwise valid received path into the RIB. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. C:Cisco weight affects only the local BGP decision and is not advertised to other routers. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. D:BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption.
Question 223 Two eBGP loopback-sourced peers cannot establish a session because default single-hop TTL cannot reach the distant loopbacks. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Check local-pref values and the selected best path on internal BGP speakers. Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Compare the full path attributes, then demonstrate the expected winner after removing the unintended override. ExplanationCorrect Answer C:Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. Other Answers A:Check local-pref values and the selected best path on internal BGP speakers. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. B:Show IPv6 unicast neighbor activation and the expected prefixes on both peers. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. D:Compare the full path attributes, then demonstrate the expected winner after removing the unintended override. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption.
Question 224 Two eBGP loopback-sourced peers cannot establish a session because default single-hop TTL cannot reach the distant loopbacks. Which lasting design or operational safeguard best prevents this particular issue from recurring? Document whether traffic-engineering policy is local-only or AS-wide before choosing attributes. Centralize egress local-preference policy and test best-path order when adding peers. Review AS-path manipulation and peering topology whenever routes traverse multiple boundaries. Include underlay reachability, TTL and update-source in loopback-peering templates. ExplanationCorrect Answer D:Include underlay reachability, TTL and update-source in loopback-peering templates. This addresses the recurring cause: Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. A targeted acceptance check is: Test TCP/179 reachability and verify Established state sourced from the intended loopbacks. Other Answers A:Document whether traffic-engineering policy is local-only or AS-wide before choosing attributes. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. B:Centralize egress local-preference policy and test best-path order when adding peers. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption. C:Review AS-path manipulation and peering topology whenever routes traverse multiple boundaries. Multihop eBGP peering over loopbacks requires packet reachability and TTL/configuration beyond a directly connected peer assumption.
Question 225 An iBGP neighbor over loopback interfaces intermittently drops while the physical path remains healthy because one router uses the transit interface as the session source. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Set the correct loopback `update-source` and peer address consistently on both ends. Use supported inbound route refresh or soft policy re-evaluation before disruptive hard resets. Do not force a MED comparison across different neighboring ASes without an explicit, supported design decision. Configure appropriate `next-hop-self` policy on the advertising boundary or distribute valid next-hop reachability. ExplanationCorrect Answer A:Set the correct loopback `update-source` and peer address consistently on both ends. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. Inspect neighbor connection details for matching local/remote addresses and stable Established uptime. Other Answers B:Use supported inbound route refresh or soft policy re-evaluation before disruptive hard resets. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. C:Do not force a MED comparison across different neighboring ASes without an explicit, supported design decision. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. D:Configure appropriate `next-hop-self` policy on the advertising boundary or distribute valid next-hop reachability. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session.
Question 226 An iBGP neighbor over loopback interfaces intermittently drops while the physical path remains healthy because one router uses the transit interface as the session source. Which technical mechanism best explains the behavior observed in this scenario? AS-path prepending advertises a longer path to remote decision makers, whose other attributes may outweigh length. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. Cisco weight affects only the local BGP decision and is not advertised to other routers. ExplanationCorrect Answer B:A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. This explains why the initial condition produces the observed failure. The direct repair is: Set the correct loopback `update-source` and peer address consistently on both ends. Validate through: Inspect neighbor connection details for matching local/remote addresses and stable Established uptime. Other Answers A:AS-path prepending advertises a longer path to remote decision makers, whose other attributes may outweigh length. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. C:A reflector advertises eligible routes according to its client relationships and filtering; client configuration changes can suppress expected reflection. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. D:Cisco weight affects only the local BGP decision and is not advertised to other routers. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session.
Question 227 An iBGP neighbor over loopback interfaces intermittently drops while the physical path remains healthy because one router uses the transit interface as the session source. After applying the correction, which verification evidence most directly demonstrates that this issue is resolved? Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. Verify policy changes take effect while neighbor Established uptime remains continuous. Inspect neighbor connection details for matching local/remote addresses and stable Established uptime. Check local-pref values and the selected best path on internal BGP speakers. ExplanationCorrect Answer C:Inspect neighbor connection details for matching local/remote addresses and stable Established uptime. This checks the affected traffic or control-plane behavior, not merely a generic up/down indicator. The underlying mechanism is: A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. Other Answers A:Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. B:Verify policy changes take effect while neighbor Established uptime remains continuous. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. D:Check local-pref values and the selected best path on internal BGP speakers. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session.
Question 228 An iBGP neighbor over loopback interfaces intermittently drops while the physical path remains healthy because one router uses the transit interface as the session source. 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. Use per-AF activation and route-policy checklists for MP-BGP sessions. Standardize stable loopback-sourced peering and test during failover. ExplanationCorrect Answer D:Standardize stable loopback-sourced peering and test during failover. This addresses the recurring cause: A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. A targeted acceptance check is: Inspect neighbor connection details for matching local/remote addresses and stable Established uptime. Other Answers A:Review attribute precedence whenever inbound path-manipulation route-maps change. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. B:Regression-test reflection and filtering for every client when modifying cluster policy. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session. C:Use per-AF activation and route-policy checklists for MP-BGP sessions. A BGP TCP connection uses the configured source IP; mismatched source and peer address can invalidate or destabilize a session.
Question 229 An upstream receives a BGP update containing its own AS in AS_PATH and the route is rejected. Which corrective action most directly resolves the documented failure without suppressing unrelated safeguards? Find the policy or topology that reintroduced the upstream's AS rather than disabling the loop check as a routine fix. Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. Set the correct loopback `update-source` and peer address consistently on both ends. Do not force a MED comparison across different neighboring ASes without an explicit, supported design decision. ExplanationCorrect Answer A:Find the policy or topology that reintroduced the upstream's AS rather than disabling the loop check as a routine fix. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. Inspect the advertised AS_PATH and ensure corrected updates no longer contain a prohibited loop. Other Answers B:Activate the peer in the appropriate BGP IPv6 AF and verify relevant IPv6 network/policy statements. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. C:Set the correct loopback `update-source` and peer address consistently on both ends. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default. D:Do not force a MED comparison across different neighboring ASes without an explicit, supported design decision. BGP's AS-path loop-prevention check rejects routes that include the receiving router's own AS by default.
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.
