Linux+ V7 IP and Interface Troubleshooting

1. A host cannot resolve example.com but can ping 8.8.8.8. What is the most likely problem?

DNS configuration is incorrect

The default route is missing

The interface is down

The firewall is blocking DNS

2. Which command reloads the network configuration without losing SSH connections on a systemd system?

Systemctl reload networking

Netplan apply

Systemctl restart systemd-networkd

Ip link set dev eth0 down && ip link set dev eth0 up

3. A system has IP 192.168.1.100/24 but cannot reach 192.168.1.1. The interface is UP. What should you verify next?

The subnet mask and gateway are correctly configured

The ARP table for the gateway MAC address

Local firewall rules blocking the gateway

All of the above

4. When troubleshooting a slow network, which tool would show packet loss and latency to a remote host?

Ping

Mtr

Traceroute

Both B and C provide useful information

5. You need to add a static route to 10.0.0.0/8 via 192.168.1.254. Which command is correct?

Ip route add 10.0.0.0/8 via 192.168.1.254

Route add -net 10.0.0.0 netmask 255.0.0.0 gw 192.168.1.254

Both A and B are valid

Neither command is correct

6. Which tool can be used to persistently configure DNS servers on a systemd system?

/etc/systemd/resolved.conf

/etc/resolv.conf

NetworkManager GUI

Both A and C

7. A static IP was configured but the system reverts to DHCP after reboot. What is the likely cause?

DHCP is still enabled in the network configuration

The interface file was not saved correctly

The network manager is overriding the static config

Any of the above could apply

8. Which command displays the ARP table to verify MAC address to IP mappings?

Arp -a or ip neigh show

Ifconfig -arp

Route -arp

Netstat -m

9. You run 'ip addr show' and see inet6 fe80::1/10 on eth0 but no inet address. What is missing?

An IPv4 address assignment

A default route

DNS configuration

The gateway address

10. Which file contains the system's DNS resolver configuration on most modern Linux distributions?

/etc/resolv.conf (or generated by systemd-resolved)

/etc/hosts

/etc/network/interfaces

/etc/hostname

11. Which command displays the current IP address configuration and interface status on a modern Linux system?

Ip addr show

Ifconfig -a

Ipconfig

Route -n

12. Which command shows detailed information about a specific interface including statistics and errors?

Ip -s link show eth0

Ethtool eth0

Nmcli device show eth0

All of the above provide useful information

13. A system shows 'RUNNING' but 'NO-CARRIER' for an interface. What does this indicate?

The driver is loaded but no physical link is detected

The IP address is not assigned

The gateway is unreachable

The interface needs to be brought up

14. After editing a netplan YAML file, which command applies the configuration without rebooting?

Netplan apply

Netplan generate

Systemctl restart networking

Both A and C

15. When using netplan on Ubuntu 20.04, where should network configuration files be placed?

/etc/netplan/

/etc/network/interfaces

/etc/sysconfig/network-scripts/

/etc/NetworkManager/

16. A system has two network cards and ping works to 192.168.1.10 but not to 10.0.0.5. What should you check first?

The routing table for a route to 10.0.0.0/24

Whether the second interface is UP

The firewall rules

DNS resolution

17. Which command adds a temporary default route via 192.168.1.1 on eth0?

Ip route add default via 192.168.1.1 dev eth0

Route add default gw 192.168.1.1

Both A and B work

Neither A nor B is correct

18. A host cannot reach a gateway at 192.168.1.1. You run 'ip route show' and see no default route. What is the most likely issue?

The default gateway is not configured

The interface is down

DNS is misconfigured

The firewall is blocking traffic

19. You suspect a network interface has an incorrect subnet mask. Which file would you check in a traditional /etc/network/ setup?

/etc/network/interfaces

/etc/sysconfig/network-scripts/

/etc/netplan/

All of the above are valid depending on the distribution

20. A user reports that their eth0 interface is DOWN. Which command would bring it back UP?

Ip link set eth0 up

Systemctl start eth0

Ifup eth0

Both A and C are correct

Linux+ V7 Troubleshooting IP and Interface Misconfiguration Quiz

1. A host cannot resolve example.com but can ping 8.8.8.8. What is the most likely problem?

2.

What first name or nickname would you like us to use?

2. Which command reloads the network configuration without losing SSH connections on a systemd system?

3. A system has IP 192.168.1.100/24 but cannot reach 192.168.1.1. The interface is UP. What should you verify next?

4. When troubleshooting a slow network, which tool would show packet loss and latency to a remote host?

5. You need to add a static route to 10.0.0.0/8 via 192.168.1.254. Which command is correct?

6. Which tool can be used to persistently configure DNS servers on a systemd system?

7. A static IP was configured but the system reverts to DHCP after reboot. What is the likely cause?

8. Which command displays the ARP table to verify MAC address to IP mappings?

9. You run 'ip addr show' and see inet6 fe80::1/10 on eth0 but no inet address. What is missing?

10. Which file contains the system's DNS resolver configuration on most modern Linux distributions?

11. Which command displays the current IP address configuration and interface status on a modern Linux system?

12. Which command shows detailed information about a specific interface including statistics and errors?

13. A system shows 'RUNNING' but 'NO-CARRIER' for an interface. What does this indicate?

14. After editing a netplan YAML file, which command applies the configuration without rebooting?

15. When using netplan on Ubuntu 20.04, where should network configuration files be placed?

16. A system has two network cards and ping works to 192.168.1.10 but not to 10.0.0.5. What should you check first?

17. Which command adds a temporary default route via 192.168.1.1 on eth0?

18. A host cannot reach a gateway at 192.168.1.1. You run 'ip route show' and see no default route. What is the most likely issue?

19. You suspect a network interface has an incorrect subnet mask. Which file would you check in a traditional /etc/network/ setup?

20. A user reports that their eth0 interface is DOWN. Which command would bring it back UP?