TCP/IP Basics

How many bits are in an IPv4 address?
A) 16
B) 32
C) 64
D) 128

B) 32 — IPv4 addresses consist of 32 bits, divided into four octets.

What is the decimal value range of an octet in IPv4?
A) 0–127
B) 0–200
C) 0–255
D) 1–255

C) 0–255 — Each octet represents 8 bits, giving 256 possible values.

What key number helps in converting binary to decimal in IP addressing?
A) 64
B) 100
C) 128
D) 256

C) 128 — Starting with 128 and halving down to 1 provides the place values for an octet.

What binary value equals decimal 255?
A) 11111110
B) 11111111
C) 10000000
D) 00000000

B) 11111111 — All ones in an octet equal 255 in decimal

What decimal value does binary 10101010 represent?
A) 160
B) 170
C) 197
D) 224

B) 170 — Adding 128 + 32 + 8 + 2 = 170.

What is the binary equivalent of decimal 224?
A) 11100000
B) 11000000
C) 11110000
D) 10000000

A) 11100000 — 224 breaks down to 128 + 64 + 32 with the rest as zeros.

What is the primary purpose of ARP (Address Resolution Protocol)?
A) Map IPv4 addresses to MAC addresses on the local network
B) Translate domain names to IP addresses
C) Securely encrypt MAC addresses before transmission
D) Route packets between different IP subnets

A) Map IPv4 addresses to MAC addresses on the local network

How does a host discover another host's MAC address when it only knows the target IP?
A) Sends an ARP broadcast asking "Who has [IP]? Tell [sender IP]"
B) Queries DNS for the MAC address
C) Contacts the default gateway to request the MAC
D) Uses ICMP echo to retrieve the MAC

A) Sends an ARP broadcast asking "Who has [IP]? Tell [sender IP]"

Which Windows command displays the system's ARP cache?
A) arp -a
B) ipconfig /all
C) netstat -r
D) nslookup -arp

A) arp -a

Why do systems store ARP entries in a cache?
A) To avoid repeatedly broadcasting ARP requests and reduce traffic/delay
B) To permanently assign MACs to IPs for all time
C) To encrypt IP-to-MAC mappings for security
D) To allow ARP to work across different subnets automatically

A) To avoid repeatedly broadcasting ARP requests and reduce traffic/delay

What happens after a host receives the ARP reply containing the target's MAC address?
A) The sender places the MAC into the Ethernet frame and transmits the frame to that MAC
B) The sender sends a DNS update to register the MAC
C) The sender reboots the NIC to apply the MAC mapping
D) The sender forwards the ARP reply to the ISP for verification

A) The sender places the MAC into the Ethernet frame and transmits the frame to that MAC

What is the primary function of a subnet mask?
A) Determine network vs host portions
B) Map IP addresses to MAC addresses
C) Assign DNS names to IPs
D) Encrypt IP traffic

A) Determine network vs host portions

What does a /24 subnet represent?
A) Mask of 24 ones (255.255.255.0)
B) Mask of 16 ones (255.255.0.0)
C) Mask of 32 ones (255.255.255.255)
D) Mask allowing 512 hosts

A) Mask of 24 ones (255.255.255.0)

How does a host decide to ARP the destination or send to its default gateway?
A) Compare destination with subnet mask; if same ARP, else use gateway
B) Always ARP every destination
C) Send all traffic directly to ISP
D) Use DNS to find MAC addresses

A) Compare destination with subnet mask; if same ARP, else use gateway

Which IP addresses are reserved inside a subnet?
A) Network ID (all zeros) and broadcast (all ones)
B) Default gateway and DHCP server only
C) Any odd-numbered hosts
D) All addresses ending in .1

A) Network ID (all zeros) and broadcast (all ones)

What is the main benefit of VLSM vs FLSM?
A) Different masks per subnet to avoid wasting addresses
B) Force the same mask for every subnet
C) Remove the need for default gateways
D) Automatically assign MACs

A) Different masks per subnet to avoid wasting addresses

How many usable hosts does a /26 subnet provide?
A) 62 usable hosts
B) 14 usable hosts
C) 254 usable hosts
D) 510 usable hosts

A) 62 usable hosts

What is the primary role of IANA?
A) Allocate and manage IP address space globally
B) Provide local network support to businesses
C) Issue domain names to individuals
D) Assign MAC addresses to devices

A) Allocate and manage IP address space globally

Who receives IP address blocks directly from IANA?
A) Regional Internet Registries (RIRs)
B) Individual home users
C) Local ISPs only
D) Web hosting companies

A) Regional Internet Registries (RIRs)

Which RIR covers Europe and parts of Asia?
A) RIPE
B) ARIN
C) APNIC
D) AFRINIC

A) RIPE

What are the first-octet ranges for Class A, B, and C addresses?
A) Class A: 0–126; Class B: 128–191; Class C: 192–223
B) Class A: 128–191; Class B: 192–223; Class C: 224–239
C) Class A: 1–50; Class B: 51–100; Class C: 101–150
D) Class A: 192–223; Class B: 128–191; Class C: 0–127

A) Class A: 0–126; Class B: 128–191; Class C: 192–223

Why was classful addressing inefficient for small organizations?
A) Minimum allocation (Class C) wasted many addresses for small needs
B) It required VLSM for every host
C) ISPs could not route classful networks
D) It forced use of IPv6

A) Minimum allocation (Class C) wasted many addresses for small needs

What is subnetting in the context of IP addressing?
A) Splitting a larger network into smaller network IDs
B) Mapping IPs to MAC addresses
C) Translating domain names to IPs
D) Combining multiple ISPs into one network

A) Splitting a larger network into smaller network IDs

What does CIDR stand for?
A) Classless Inter-Domain Routing
B) Classful Internet Distribution Route
C) Common IP Domain Routing
D) Centralized Internet Address Registry

A) Classless Inter-Domain Routing

What subnet mask corresponds to a /25 prefix?
A) 255.255.255.128
B) 255.255.255.0
C) 255.255.255.192
D) 255.255.255.64

A) 255.255.255.128

How many usable hosts does a /24 subnet provide?
A) 254 usable hosts
B) 256 usable hosts
C) 126 usable hosts
D) 62 usable hosts

A) 254 usable hosts

How many usable hosts does a /25 subnet provide?
A) 126 usable hosts
B) 254 usable hosts
C) 62 usable hosts
D) 30 usable hosts

A) 126 usable hosts

If you change a /24 to a /26, how many subnets do you create from the original /24?
A) 4 subnets
B) 2 subnets
C) 8 subnets
D) 16 subnets

A) 4 subnets

What is the formula to calculate usable hosts for a given prefix?
A) 2^(32 - prefix) - 2
B) 2^(prefix) - 2
C) 2^(32 - prefix)
D) 2^(prefix)

A) 2^(32 - prefix) - 2 (total addresses minus network and broadcast)

Which CIDR prefix provides 6 usable hosts?
A) /29 (6 usable hosts)
B) /28 (14 usable hosts)
C) /30 (2 usable hosts)
D) /26 (62 usable hosts)

A) /29 (6 usable hosts)

Given the network 199.44.6.80/28, which range lists the usable host addresses?
A) 199.44.6.81–199.44.6.94
B) 199.44.6.80–199.44.6.95
C) 199.44.6.82–199.44.6.93
D) 199.44.6.84–199.44.6.97

A) 199.44.6.81–199.44.6.94

Why do servers (web, email, game) typically require static IP addresses?
A) Static IPs provide fixed public addresses so external clients can reliably reach the server
B) Static IPs automatically encrypt traffic for servers
C) Static IPs allow servers to change address frequently for load balancing
D) Static IPs are always provided free by ISPs

A) Static IPs provide fixed public addresses so external clients can reliably reach the server

If you need four public IP addresses for servers, which smallest CIDR block should you request?
A) /29 (6 usable hosts)
B) /30 (2 usable hosts)
C) /28 (14 usable hosts)
D) /27 (30 usable hosts)

A) /29 (6 usable hosts)

When an ISP supplies a small block of static IPs, what address do they commonly reserve?
A) One address for their upstream router (the gateway)
B) One address for the customer’s DHCP server
C) All addresses are given to the customer with no reservation
D) One address is reserved for DNS only

A) One address for their upstream router (the gateway)

What does DHCP do?
A) Automatically assigns IP settings to clients
B) Maps IP addresses to MAC addresses
C) Assigns DNS names to IPs
D) Encrypts IP traffic

A) Automatically assigns IP settings to clients

A) Discover → Offer → Request → Ack
B) Offer → Discover → Request → Ack
C) Discover → Request → Offer → Ack
D) Request → Discover → Offer → Ack

A) Discover → Offer → Request → Ack

What is a DHCP reservation?
A) Linking a MAC address to a specific IP
B) Temporary IP lease from the pool
C) A relay that forwards DHCP broadcasts
D) An IPv6 autoconfiguration method

A) Linking a MAC address to a specific IP

Why use a DHCP relay agent (IP helper)?
A) Forward DHCP broadcasts across subnets
B) Encrypt DHCP traffic between networks
C) Assign static IP addresses remotely
D) Provide DNS resolution for clients

A) Forward DHCP broadcasts across subnets

What does SLAAC do on IPv6?
A) Hosts auto-generate IPv6 addresses using EUI-64
B) Servers assign IPv6 via DHCPv6
C) Translate IPv6 to IPv4 automatically
D) Use DHCPv4 for IPv6 addresses

A) Hosts auto-generate IPv6 addresses using EUI-64

Which DHCP settings define the IP range and lease duration?
A) Address scope and lease time
B) Reservation table and MAC filter
C) IP helper and relay address
D) SLAAC and EUI-64 options

A) Address scope and lease time

Which IPv4 ranges are private (non-routable on the Internet)?
A) 10.0.0.0/8
B) 172.16.0.0–172.31.255.255
C) 192.168.0.0/16
D) All three are private ranges

D) All three are private ranges — 10/8, 172.16–172.31, and 192.168/16 are reserved for private networks.

What is the standard IPv4 loopback address?
A) 127.0.0.1
B) 169.254.0.1
C) ::1
D) 0.0.0.0

A) 127.0.0.1 — The canonical IPv4 loopback address; 127/8 is reserved for loopback.

What is the IPv6 loopback address?
A) ::1
B) 127.0.0.1
C) fe80::1
D) fd00::1

A) ::1 — The single-address IPv6 loopback equivalent to IPv4's 127.0.0.1.

Which range indicates an APIPA (Automatic Private IP Addressing) address?
A) 169.254.0.0/16
B) 10.0.0.0/8
C) 192.168.0.0/16
D) 127.0.0.0/8

A) 169.254.0.0/16 — APIPA addresses (169.254.x.x) are auto-assigned when DHCP fails and allow local-only connectivity.

Why are private IP addresses used?
A) Used only for internal networks and not routable on the Internet
B) Assigned by IANA for public routing
C) Reserved specifically for loopback testing
D) Only usable by DHCP clients

A) Used only for internal networks and not routable on the Internet — Private addresses conserve public space and require NAT to access the Internet.

How do devices using private IPs reach the Internet?
A) A NAT device on the gateway/router translates private to public addresses
B) ISPs route private addresses directly
C) ARP converts private to public addresses
D) SLAAC automatically provides public addresses

A) A NAT device on the gateway/router translates private to public addresses — NAT on the gateway maps internal private addresses to a public IP for Internet communication.

What is a common Windows behavior when a duplicate IP address is detected?
A) Windows shows an error and attempts to fix it (may switch to DHCP)
B) Windows silently ignores the conflict and continues normally
C) Windows immediately reboots the machine
D) Windows changes the MAC address automatically

A) Windows shows an error and attempts to fix it (may switch to DHCP)

What is a frequent cause of duplicate MAC addresses in a virtualized environment?
A) Cloning virtual machines and copying the same MAC without changing it
B) DHCP assigning the same MAC to two hosts
C) The switch rewriting MAC addresses randomly
D) A corrupted ARP cache on the router

A) Cloning virtual machines and copying the same MAC without changing it

What symptom indicates an incorrect default gateway on a host?
A) Host can reach local resources but cannot access the Internet or other subnets
B) Host cannot communicate with other hosts on the same LAN at all
C) Host receives APIPA address immediately
D) Host's MAC address disappears from the switch table

A) Host can reach local resources but cannot access the Internet or other subnets

What problem can a mismatched subnet mask between two hosts cause?
A) One-way or asymmetric connectivity where one host can ping the other but not vice versa
B) Immediate DHCP reservation conflicts for all hosts
C) Switch ports shutting down due to loop detection
D) The router assigning new MAC addresses to hosts

A) One-way or asymmetric connectivity where one host can ping the other but not vice versa

What does an IP of 169.254.x.x on a host typically indicate?
A) The host could not reach a DHCP server and assigned itself an APIPA address
B) The host has a valid public static IP assigned by the ISP
C) The host's gateway is set incorrectly to .254
D) The host is using IPv6 instead of IPv4

A) The host could not reach a DHCP server and assigned itself an APIPA address

Which basic commands are most useful first steps to diagnose IP configuration issues on Windows and Linux?
A) ipconfig (Windows) or ifconfig (Linux) to view settings, and ping/traceroute to test connectivity
B) nslookup only, because it shows IP mappings
C) format C: to reset the network stack
D) arp -d on every device to clear caches before testing

A) ipconfig (Windows) or ifconfig (Linux) to view settings, and ping/traceroute to test connectivity