Certification793 problems· 22 reviewed

CCNA

793 incident response problems that help with CCNA prep.

All problems (793)

NETWORK-1256Two OSPF neighbors stay in ExStart or ExchangeA routing change enables OSPF between devices that can ping each other but never complete adjacency formation.NetworkIntermediate16 minPro NETWORK-1276A backup trunk wakes up during maintenance and causes root-inconsistent blockingA redundancy test activates a little-used link and suddenly one segment is blocked or err-disabled by spanning-tree policy.NetworkAdvanced17 minPro NETWORK-1291A BGP session stays up but the preferred path disappearsA routing optimization on a reflector leads one downstream edge to change behavior without any session flap.NetworkAdvanced17 minPro NETWORK-1295A NAT exemption survives on paper but one backup path still translatesA VPN path works on the active firewall and fails only after failover or during HA testing.NetworkAdvanced17 minPro NETWORK-148A PBR next-hop tracks the firewall IP, but the firewall can still answer ARP while the service process behind it is deadThe tracked object remains reachable even though the real dependency has failed.NetworkAdvanced17 minPro NETWORK-1297A PMTUD issue affects only DNSSEC responsesUsers resolve common domains correctly and validation-heavy DNS workflows fail in one network path.NetworkAdvanced17 minPro NETWORK-369A QoS policy marks the right classes while tunnel overhead changed and one class now fragments or drops before the shaped queue ever sees it during a staged decommissionClassification is correct, but the packet size math no longer fits the path. The service still works through the primary path, but one dependency only fails when the old component is finally drained away.NetworkAdvanced17 minPro NETWORK-1299A route reflector cluster stays healthy but one edge blackholes trafficA route policy cleanup on a reflector changes forwarding behavior without dropping any BGP sessions.NetworkAdvanced17 minPro NETWORK-330A route summary survives while every specific path behind it is now gone and traffic keeps choosing the black hole during a failover rehearsalAggregation stays healthy after the real forwarding options disappeared. Normal traffic masked the issue until the standby or alternate path became active under rehearsal conditions.NetworkIntermediate17 minPro NETWORK-121A transit interface was left out of passive-interface default exceptions, and a rogue OSPF adjacency forms during an access switch replacementThe underlay works until maintenance introduces a neighbor on a segment that should never have participated in routing.NetworkAdvanced17 minPro NETWORK-1227A trunk passes most VLANs but one voice segment still failsA cross-vendor trunk migration leaves data VLANs healthy while one voice or management path becomes unstable.NetworkIntermediate17 minPro NETWORK-1207Native VLAN assumptions hide the real issueA multi-vendor trunk stays healthy on paper, but one service VLAN never crosses it.NetworkIntermediate17 minPro NETWORK-1274OSPF neighbors form but one network never appearsAn operator proves OSPF is up and still cannot explain why only one important network is absent downstream.NetworkAdvanced17 minPro NETWORK-1261A BGP policy stops preferring the intended upstreamNetwork incident scenario used for structured troubleshooting practice.NetworkAdvanced18 minPro NETWORK-1266A BGP policy stops preferring the intended upstreamAn operator refactors an inbound route-map and later discovers traffic stopped preferring the expected provider without the BGP session ever dropping.NetworkAdvanced18 minPro NETWORK-1246A failover appears clean on the routers but users still blackholeA maintenance failover completes and a subset of endpoints remain broken until caches naturally refresh.NetworkAdvanced18 minPro NETWORK-1233A failover design works in tests but production users still blackholeA failover event completes and a subset of clients remain broken even though the new active gateway is online and forwarding.NetworkAdvanced18 minPro NETWORK-1241A failover path looks clean but one segment still blackholesA maintenance failover succeeds on the routers, but a subset of users remain broken until cache state ages out or is refreshed.NetworkAdvanced18 minPro NETWORK-204A failover signal tracks device liveness while the service behind it is already gone during a failover rehearsalThe route follows a reachable box instead of the actual service dependency. Normal traffic masked the issue until the standby or alternate path became active under rehearsal conditions.NetworkAdvanced18 minPro NETWORK-1285A firewall cluster syncs configuration but not connection state, so asymmetric return traffic after failover only breaks one long-lived application protocolPolicies match and sessions establish initially, yet one application fails after failover because session state was not replicated the way operators assumed.NetworkAdvanced18 minPro