Network Configuration & Troubleshooting Flashcards

Which command permanently sets the hostname to 'prod-server-01' on a systemd-based Linux system?

Answer: hostnamectl set-hostname prod-server-01

'hostnamectl set-hostname' updates /etc/hostname and the running system hostname atomically without requiring a reboot.

A packet sent to 8.8.8.8 is dropped at hop 5 during a traceroute. What does this mean?

Answer: ICMP is blocked at hop 5, but the destination may still be reachable

Many routers deprioritize or block ICMP TTL-exceeded responses, so a traceroute timeout at a hop doesn't mean the destination is unreachable.

Which command creates a VLAN interface tagged as VLAN 100 on top of eth0?

Answer: ip link add link eth0 name eth0.100 type vlan id 100

'ip link add link eth0 name eth0.100 type vlan id 100' creates an 802.1Q VLAN subinterface using iproute2.

What does the 'nft list ruleset' command do?

Answer: Displays the complete nftables ruleset including tables, chains, and rules

'nft list ruleset' outputs the full nftables configuration including all tables, chains, and rules in a readable format.

A DHCP client is not receiving an IP address. After confirming the DHCP server is running, what should you check next on the client?

Answer: Whether the client's NIC is up and sending DHCPDISCOVER broadcasts

DHCP begins with the client broadcasting DHCPDISCOVER; verifying the NIC is up and the broadcast is sent confirms the client side is working.

Which command shows detailed statistics for interface eth0, including TX/RX errors and dropped packets?

Answer: ip -s link show eth0

'ip -s link show eth0' displays per-interface statistics including transmitted/received bytes, errors, and drops.

You need to test DNS resolution for the hostname 'api.example.com' against a specific DNS server at 1.1.1.1. Which command does this?

Answer: dig @1.1.1.1 api.example.com

'dig @server hostname' queries the specified DNS server directly, bypassing /etc/resolv.conf settings.