Linux Networking 3 — Questions and Answers
Question 1: What does CIDR notation `/24` indicate about a network?
- The first 24 bits are the network portion (Correct answer)
- There are 24 available hosts
- The subnet has 24 subnets
- The TTL is set to 24
Correct answer: The first 24 bits are the network portion
In CIDR notation, `/24` means 24 bits are used for the network prefix, leaving 8 bits for host addresses (254 usable hosts).
Question 2: Which command would you use to test if a remote host is reachable at the network layer?
- ping (Correct answer)
- curl
- netstat
- nslookup
Correct answer: ping
`ping` sends ICMP echo request packets to test basic connectivity and measure round-trip time to a host.
Question 3: What is the loopback IP address in IPv4?
- 127.0.0.1 (Correct answer)
- 192.168.0.1
- 10.0.0.1
- 0.0.0.0
Correct answer: 127.0.0.1
127.0.0.1 is the IPv4 loopback address (also `localhost`) used by the system to communicate with itself.
Question 4: Which tool scans for open ports and services on a target host?
- nmap (Correct answer)
- dig
- ss
- mtr
Correct answer: nmap
`nmap` (Network Mapper) is a widely-used tool for port scanning, service detection, and network discovery.
Question 5: What does the ARP protocol resolve?
- IP addresses to MAC addresses (Correct answer)
- Hostnames to IP addresses
- MAC addresses to port numbers
- IP addresses to domain names
Correct answer: IP addresses to MAC addresses
ARP (Address Resolution Protocol) maps an IPv4 address to the corresponding hardware (MAC) address on a local network segment.
Question 6: Which `netstat` flag shows only listening sockets?
- -l (Correct answer)
- -a
- -n
- -p
Correct answer: -l
The `-l` flag in `netstat` (or `ss -l`) filters output to display only sockets in the listening state.
Question 7: What is the default gateway's role in a network?
- Routes traffic destined for networks outside the local subnet (Correct answer)
- Assigns IP addresses via DHCP
- Resolves hostnames to IP addresses
- Filters packets using firewall rules
Correct answer: Routes traffic destined for networks outside the local subnet
The default gateway is the router that handles traffic destined for IP addresses not in the local subnet.
Linux Networking 3
What does CIDR notation `/24` indicate about a network?