Network Diagnostics

During a network outage, you observe that devices in one VLAN can communicate with each other but not with devices in another VLAN. What could be the most likely cause?

You notice intermittent connectivity issues on a specific subnet. After checking the switch, you find a high number of CRC errors. What is the most probable cause?

A network technician replaced a switch, and now some devices are not accessible. All connections and configurations appear correct. What should be checked first?

After configuring a new ACL on a router, users report they can no longer access the internet. Which command can help diagnose the problem?

Your network monitoring tool reports high CPU usage on a router. Which of the following could be a cause?

You suspect a routing loop is occurring in your network. Which command can help verify this issue?

Users in one office complain about slow network performance. You suspect a broadcast storm. Which metric should you check on the switch?

A switchport shows as "err-disabled." Which command can you use to re-enable the port?

While troubleshooting a routing issue, you notice that one of the OSPF routers has an empty OSPF neighbor table. What might be the cause?

Users report that they cannot reach a server located in a different subnet. The server responds to pings from its local subnet but not from others. What could be the cause?

A network engineer observes that a newly connected device is not receiving a DHCP address. Which of the following is a potential cause?

A network segment is experiencing high latency. Upon inspection, you find that one device is sending an unusually high number of ICMP packets. What type of issue does this indicate?

You find that a switch's MAC address table is filling up very quickly, which causes intermittent connectivity issues. What could be the reason?

During an audit, it is found that an important VLAN is not propagating to a new switch. Which command would help diagnose the issue?

Users report that they can’t access certain websites, but other sites work fine. Which tool would you use first to diagnose the issue?

A router is not forming an EIGRP neighbor relationship with a newly added router. What is a potential cause?

Network devices are configured for SNMP monitoring, but data collection fails intermittently. What could be the most likely cause?

After a network upgrade, users report connectivity issues to a remote site. You suspect MTU size mismatches. Which command would help verify this?

Users report slow access to an application server. Network monitoring shows high traffic on the server’s interface. Which type of traffic should you look for to identify a potential issue?

A network technician replaced a faulty switch, but now the new switch doesn’t have the correct VLAN information. What could be the reason?

You notice that the OSPF cost for a particular link has changed unexpectedly. What is a possible cause?

A network device shows an excessive number of input errors. What could be the cause?

A newly configured BGP session is not establishing. Which command can you use to troubleshoot the issue?

After a network change, some users cannot access a particular website. A packet capture shows that the DNS query is successful, but the TCP handshake fails. What is a likely cause?

You observe that an interface on a switch is constantly flapping. What should be checked first?

Users complain about slow response times from a server. The server is in the same VLAN as the users. What should be checked first?

A network engineer is troubleshooting a high collision rate on a segment. What is a probable cause?

A device is not appearing in the neighbor table of a directly connected router running EIGRP. What is the likely cause?

You observe that a specific VLAN is not passing traffic. What command can you use to verify its status on a switch?

Users report that they cannot access the network after a switch reboot. Which of the following might be the cause?

You are troubleshooting a network issue and suspect a duplicate IP address. Which command can help you find the conflicting device?

You notice that a static route in the routing table has disappeared. What could be the reason?

After adding a new switch to the network, you find that certain devices are no longer reachable. What could be a probable cause?

A network device shows high memory usage. Which command would you use to identify the process consuming the most memory?

While troubleshooting a VoIP issue, you find excessive jitter on the network. What could be the cause?

You are troubleshooting a site-to-site VPN connection and notice that the tunnel is up, but traffic is not passing through. What could be a potential cause?

A switchport configured for 802.1X authentication is not allowing a device to connect. What is the likely cause?

You are troubleshooting a multicast issue in a network. Which command can help verify if a router is receiving multicast traffic?

After a power outage, certain devices are not reachable. The devices are connected to a switch, which appears to be functioning normally. What should you check first?

A network segment is experiencing intermittent connectivity issues. You suspect a faulty network cable. What tool would you use to confirm this?

You are troubleshooting an issue where users can ping a server but cannot access its web services. What is the most likely cause?

A network administrator reports that OSPF routes are not being advertised to a specific neighbor. What command would help diagnose the issue?

A network engineer notices that a router’s routing table is missing routes that should be there. What command can help determine if the routes are being filtered?

You notice that a switchport connected to an IP phone shows a large number of collisions. What is a potential cause?

A network engineer sees that an interface is down/down on a router. What could be a probable cause?

You suspect a broadcast storm in the network. Which command can help identify if broadcast traffic is causing the issue?

A network engineer finds that HSRP is not working as expected. What could be a potential cause?

After configuring port security on a switch, a port goes into err-disabled state. What command can help identify the reason?

Users report that they cannot access a file server after a routing protocol change. The server’s IP address is still reachable via ping. What should you check next?

A router is not forwarding packets from a specific subnet. The routing table appears correct. What could be the cause?