CCNA
793 incident response problems that help with CCNA prep.
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All problems (793)
NETWORK-1280A firewall migration preserves ACL intent but one application still failsA firewall migration keeps most services working and leaves one application path failing in a way the old ACL logic did not predict.NetworkAdvanced18 minProNETWORK-306A QoS trust boundary changed on one edge while policy-map assumptions on the WAN handoff still reflect the old marking point during a failover rehearsalMarking is correct in one segment and wrong by the time traffic reaches the WAN policy decision. Normal traffic masked the issue until the standby or alternate path became active under rehearsal conditions.NetworkAdvanced18 minProNETWORK-1293A route leaking design works until a maintenance reloadInter-VRF reachability is stable for months and fails only after a planned reload or software update.NetworkAdvanced18 minProNETWORK-1289A route reflects correctly inside the core but one edge never installs itA route is visible at the route-reflector and on several peers, but one edge still never installs it after a prior prefix surge incident.NetworkAdvanced18 minProNETWORK-511A static summary route is valid (Rollout Stuck)A static summary route is valid (Rollout Stuck) focuses on Routing And Failover Paths and asks the reader to isolate Rollout Stuck in Cisco. 실무에서는 rollout-stuck 이슈를 볼 때 DNS, 라우팅, ACL/방화벽, 목적지 응답을 계층별로 잘라서 확인하면 장애 구간을 훨씬 빠르게 좁힐 수 있습니다.NetworkIntermediate18 minProNETWORK-1251An HSRP failover looks clean on the routers but clients still blackholeA maintenance failover succeeds on the routers, but a portion of users remain offline until cache state ages out or is forced to refresh.NetworkAdvanced18 minProNETWORK-1281An OSPF adjacency remains stuck in ExStartAn OSPF adjacency remains stuck in ExStart focuses on ospf-operations and asks the reader to isolate the key signal in Cisco. Protocol failures sometimes follow the effective data-plane MTU, not the configured value visible in the template.NetworkAdvanced18 minProNETWORK-1216HSRP failover happens but some clients still reach the old MACAn HSRP pair switches roles during maintenance and some users remain blackholed even though the new active gateway is up.NetworkAdvanced18 minProNETWORK-1257ip ospf mtu-ignore brings the adjacency up, but later large LSUs still failOperators apply mtu-ignore to stop an adjacency flap and later discover certain routes still never arrive correctly.NetworkAdvanced18 minProNETWORK-1226OSPF neighbors remain in ExStartTwo routers see each other and even exchange hellos, but the adjacency sticks in ExStart over a tunnel interface.NetworkAdvanced18 minProNETWORK-1206OSPF neighbors remain stuck in ExStartTwo routers can see each other but never reach Full adjacency after an interface template change.NetworkAdvanced18 minProNETWORK-571A static summary route is valid (Rollout Stuck)A static summary route is valid (Rollout Stuck) focuses on Routing And Failover Paths and asks the reader to isolate Rollout Stuck in Cisco. 실무에서는 rollout-stuck 이슈를 볼 때 DNS, 라우팅, ACL/방화벽, 목적지 응답을 계층별로 잘라서 확인하면 장애 구간을 훨씬 빠르게 좁힐 수 있습니다.NetworkIntermediate19 minProNETWORK-1221VLAN trunks look healthy but one segment goes root-inconsistentA campus segment works for most VLANs but one path blocks after a trunk template change.NetworkAdvanced19 minProNETWORK-631A static summary route is valid (Rollout Stuck)A static summary route is valid (Rollout Stuck) focuses on Routing And Failover Paths and asks the reader to isolate Rollout Stuck in Cisco. 실무에서는 rollout-stuck 이슈를 볼 때 DNS, 라우팅, ACL/방화벽, 목적지 응답을 계층별로 잘라서 확인하면 장애 구간을 훨씬 빠르게 좁힐 수 있습니다.NetworkIntermediate20 minProNETWORK-1230STP root placement looks intentional but one access stack goes root-inconsistentA backup uplink that is rarely used becomes active during maintenance and one stack immediately enters a root-inconsistent or blocked state.NetworkAdvanced20 minProNETWORK-1188Interface flap alarms hide that one side still negotiates the wrong speed and duplex profilePacket loss and churn appear during intermittent link events because one interface reverted to a different negotiation profile after maintenance.NetworkAdvanced21 minProNETWORK-1208Stateful firewall drops only the return pathA service opens outbound sessions successfully but return packets come back through another path and get dropped.NetworkAdvanced21 minProNETWORK-1191Trunk link stays up but one VLAN is black-holedA trunk link is rebuilt after maintenance. Community threads suggest checking tagging expectations, and it turns out one side still treats a management VLAN as native.NetworkIntermediate21 minProNETWORK-690A static summary route is valid (Rollout Stuck)A static summary route is valid (Rollout Stuck) focuses on Routing And Failover Paths and asks the reader to isolate Rollout Stuck in Cisco. 실무에서는 rollout-stuck 이슈를 볼 때 DNS, 라우팅, ACL/방화벽, 목적지 응답을 계층별로 잘라서 확인하면 장애 구간을 훨씬 빠르게 좁힐 수 있습니다.NetworkIntermediate22 minProNETWORK-1202Asymmetric routing keeps stateful firewall sessions failing after one return path changed quietlyForward traffic reaches the service, but responses traverse another path and hit a stateful filter that never saw the original session setup.NetworkAdvanced22 minPro