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Junior Network Administrator practice questions

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Question 1Network Fundamentals and Models

A workstation sends a frame to a server on the same VLAN. Which address does the workstation place in the destination field of the Ethernet header it builds?

  1. The MAC address of the default gateway
  2. The MAC address of the server's network interface Correct answer.
  3. The IP address of the default gateway
  4. The broadcast MAC address FF:FF:FF:FF:FF:FF

Explanation

Within a single VLAN the hosts share a broadcast domain, so the sender resolves the destination IP to the destination MAC with ARP and addresses the frame directly to the server. The gateway MAC is used only when the destination IP is off-subnet, and the broadcast address is not used for unicast delivery.

Question 2Network Fundamentals and Models

Which layer of the OSI model is responsible for logical addressing and path selection between networks?

  1. Network layer Correct answer.
  2. Transport layer
  3. Data link layer
  4. Session layer

Explanation

The network layer handles logical (IP) addressing and routing decisions that move packets between different networks. The data link layer deals with local frame delivery, the transport layer with end-to-end segments, and the session layer with dialog management.

Question 3Network Fundamentals and Models

Which TCP/IP model layer corresponds most closely to the OSI data link and physical layers combined?

  1. Transport layer
  2. Network access layer Correct answer.
  3. Application layer
  4. Internet layer

Explanation

The four-layer TCP/IP model merges OSI layers 1 and 2 into a single network access (link) layer that covers physical transmission and local framing. The internet layer maps to OSI layer 3 and the transport layer to OSI layer 4.

Question 4Network Fundamentals and Models

A switch receives a unicast frame whose destination MAC address is not in its MAC address table. What does the switch do with the frame?

  1. It holds the frame until the destination host sends a frame of its own
  2. It discards the frame and logs the unknown address
  3. It floods the frame out of all ports in the same VLAN except the ingress port Correct answer.
  4. It forwards the frame only to the uplink toward the default gateway

Explanation

Unknown unicast frames are flooded within the VLAN so the destination can be reached without waiting for a table entry. The switch learns the source MAC from the same frame, so subsequent replies can be forwarded directly.

Question 5Network Fundamentals and Models

Which address range is reserved for IPv4 link-local (APIPA) addressing?

  1. 172.16.0.0/12
  2. 169.254.0.0/16 Correct answer.
  3. 10.0.0.0/8
  4. 192.168.0.0/16

Explanation

The 169.254.0.0/16 range is set aside for link-local autoconfiguration, used when a DHCP server cannot be reached. The other ranges listed are private addresses assigned by DHCP or statically.

Question 6Network Fundamentals and Models

Which protocol resolves an IPv4 address to a MAC address on a local network?

  1. ARP Correct answer.
  2. DNS
  3. ICMP
  4. DHCP

Explanation

ARP broadcasts a request asking which host owns a given IPv4 address and receives the corresponding MAC address in reply. DNS resolves names to addresses, DHCP assigns configuration, and ICMP carries error and diagnostic messages.

Question 7Network Fundamentals and Models

What is the primary purpose of VLANs on a managed switch?

  1. To encrypt traffic between switches
  2. To increase the speed of uplink ports
  3. To divide one physical switch into multiple separate broadcast domains Correct answer.
  4. To assign IP addresses to connected hosts automatically

Explanation

A VLAN logically segments a switch so that each VLAN is its own broadcast domain, containing broadcasts and improving traffic control. Encryption, link speed, and address assignment are handled by other mechanisms.

Question 8Network Fundamentals and Models

Which device forwards packets between different IP subnets by consulting a routing table?

  1. Hub
  2. Layer 2 switch
  3. Access point
  4. Router Correct answer.

Explanation

A router makes forwarding decisions per packet based on destination network entries in its routing table, which is what moves traffic between subnets. A switch forwards frames within a subnet, a hub repeats signals, and an access point bridges wireless clients.

Question 9Network Fundamentals and Models

A host has the address 192.168.10.130/26. What is the network address of its subnet?

  1. 192.168.10.64
  2. 192.168.10.192
  3. 192.168.10.0
  4. 192.168.10.128 Correct answer.

Explanation

A /26 mask leaves 6 host bits, so each subnet contains 64 addresses and boundaries fall at multiples of 64: 0, 64, 128, 192. The address 130 lies in the block beginning at 128, making 192.168.10.128 the network address.

Question 10Network Fundamentals and Models

A network engineer needs 60 usable host addresses per subnet. Which prefix length is the most efficient choice?

  1. /28
  2. /26 Correct answer.
  3. /27
  4. /25

Explanation

A /26 provides 64 addresses, of which 62 are usable after removing the network and broadcast addresses, which covers 60 hosts with minimal waste. A /25 would also work but wastes more addresses, while /27 and /28 provide too few hosts.

Question 11Network Fundamentals and Models

Which statement correctly describes the difference between TCP and UDP?

  1. TCP operates at the network layer and UDP at the transport layer
  2. UDP guarantees delivery while TCP does not
  3. TCP provides ordered, acknowledged delivery while UDP sends datagrams without acknowledgments Correct answer.
  4. TCP is connectionless and UDP is connection-oriented

Explanation

TCP establishes a connection, sequences segments, and acknowledges data so lost segments can be retransmitted, whereas UDP sends independent datagrams with no delivery guarantee. Both protocols operate at the transport layer.

Question 12Network Fundamentals and Models

Which range of port numbers is classified as the well-known port range by IANA?

  1. 1024 through 65535
  2. 49152 through 65535
  3. 1024 through 49151
  4. 0 through 1023 Correct answer.

Explanation

IANA divides ports into well-known (0 through 1023), registered (1024 through 49151), and dynamic or private (49152 through 65535). Services such as HTTP on 80 and SSH on 22 sit in the well-known range.

Question 13Network Fundamentals and Models

A user reports that a laptop configured with a static IP address in the correct subnet cannot reach any host, including the gateway. Which troubleshooting step should be performed first?

  1. Verify the subnet mask and default gateway settings on the laptop Correct answer.
  2. Renew the DHCP lease on the laptop
  3. Reboot the core switch
  4. Replace the network cable

Explanation

When a static configuration is in place, an incorrect mask or gateway is the most likely cause of total unreachability, so the configuration should be verified before swapping hardware. The laptop uses no DHCP lease, making renewal irrelevant.

Question 14Network Fundamentals and Models

Which field in an IPv4 header prevents packets from looping indefinitely between routers?

  1. Fragment offset
  2. Time to Live Correct answer.
  3. Identification
  4. Header checksum

Explanation

The Time to Live field is decremented by each router, and a packet whose value reaches zero is discarded, which stops routing loops from persisting. The checksum protects header integrity, while identification and fragment offset support reassembly.

Question 15Network Fundamentals and Models

Which characteristic distinguishes a collision domain from a broadcast domain?

  1. A collision domain is bounded by routers, and a broadcast domain is bounded by switches
  2. A collision domain includes all devices sharing a segment where frames can collide, while a broadcast domain includes all devices that receive a broadcast frame Correct answer.
  3. A collision domain is always larger than a broadcast domain
  4. A broadcast domain exists only on wireless networks

Explanation

A collision domain covers devices whose transmissions can physically interfere, which switches divide per port. A broadcast domain covers devices that receive a given broadcast, which switches keep intact unless VLANs or routers separate them.

Question 16Network Fundamentals and Models

What does the address 2001:db8::1/64 represent?

  1. A global unicast IPv6 address Correct answer.
  2. An IPv6 loopback address
  3. An IPv4-compatible address
  4. An IPv6 multicast address

Explanation

Addresses beginning with 2001:db8 belong to the documentation prefix within the global unicast range, and the /64 indicates a standard subnet prefix. Multicast addresses start with ff00::/8 and the loopback is ::1.

Question 17Network Fundamentals and Models

A technician connects two switches with a single cable and both ports are set to auto-negotiate speed and duplex. Which outcome is most likely if the negotiation fails?

  1. The link automatically becomes a trunk
  2. Both links operate at full duplex without issue
  3. The switches form a routing adjacency
  4. A duplex mismatch occurs, causing collisions and degraded throughput Correct answer.

Explanation

When autonegotiation fails on one side, one end may fall back to half duplex while the other stays at full duplex, producing late collisions and poor performance. Duplex settings must match on both ends of a link.

Question 18Network Fundamentals and Models

Which statement best describes how a router handles a packet whose destination network is not present in its routing table and no default route exists?

  1. It floods the packet out of every interface
  2. It forwards the packet to the nearest switch
  3. It drops the packet and may return an ICMP destination unreachable message Correct answer.
  4. It holds the packet until a route is learned

Explanation

Without a matching route or default route, the router has no path to the destination and discards the packet, often notifying the source with an ICMP unreachable message. Routers do not flood packets across interfaces or wait indefinitely for routes.

Question 19Network Fundamentals and Models

An administrator wants to verify that a host's default gateway is reachable at the network layer. Which command is appropriate?

  1. arp -a
  2. ipconfig /all
  3. ping 192.168.1.1 Correct answer.
  4. netstat -n

Explanation

Ping sends ICMP echo requests to the specified address and reports whether replies arrive, which tests layer 3 reachability to the gateway. The other commands display local configuration or connection tables without testing reachability.

Question 20Network Fundamentals and Models

Which statement about the TCP three-way handshake is correct?

  1. The handshake uses UDP to establish the connection before TCP takes over
  2. The server initiates the handshake with a SYN to the client's ephemeral port
  3. The client sends SYN, the server replies with SYN-ACK, and the client responds with ACK Correct answer.
  4. The client sends ACK, the server replies with SYN, and the client responds with SYN-ACK

Explanation

TCP connection setup begins with a SYN from the initiator, followed by a SYN-ACK from the responder that acknowledges the first sequence number and supplies its own, and ends with an ACK from the initiator. This exchange synchronizes sequence numbers in both directions.

Question 21Network Fundamentals and Models

A company uses the 172.20.0.0/16 network and needs subnets supporting at least 500 hosts each. Which prefix length provides the smallest sufficient subnet?

  1. /22
  2. /21
  3. /23 Correct answer.
  4. /24

Explanation

A /23 leaves 9 host bits, yielding 512 addresses and 510 usable hosts, which meets the 500-host requirement with the least waste. A /24 yields only 254 usable hosts, while /22 and /21 exceed the requirement and waste space.

Question 22Network Fundamentals and Models

Two hosts on the same VLAN have addresses 10.1.1.10/24 and 10.1.2.20/24. What happens when the first host pings the second?

  1. The ping succeeds because both hosts are in the same VLAN
  2. The first host broadcasts an ARP request for 10.1.2.20 and receives a reply
  3. The switch rewrites the destination IP address to keep the traffic local
  4. The first host sends the packet to its default gateway, which may drop it if no route exists Correct answer.

Explanation

The /24 masks place the hosts in different subnets, so the sender treats the destination as remote and forwards to its gateway. If the gateway lacks a route to 10.1.2.0/24, the packet is dropped even though both hosts share a VLAN.

Question 23Network Fundamentals and Models

A network uses a single /24 subnet for 200 workstations and one server. Broadcast traffic is degrading performance. Which change best reduces the broadcast domain size while preserving connectivity?

  1. Replace the switch with a hub
  2. Increase the MTU on all interfaces
  3. Split the subnet into two VLANs and route between them Correct answer.
  4. Assign all hosts static addresses

Explanation

Creating additional VLANs divides the broadcast domain, and a router or Layer 3 switch forwards unicast traffic between the segments. A hub would worsen collisions, and MTU or static addressing does not reduce broadcast scope.

Question 24Network Fundamentals and Models

A host configured with 192.168.5.200/27 reports that it cannot reach any other device on its subnet. Which address assignment explains the failure?

  1. The host is using the broadcast address of a different subnet
  2. The host is using a valid host address in the 192.168.5.192/27 subnet
  3. The host is using an address outside the private range
  4. The host is using the network address of its subnet Correct answer.

Explanation

With a /27 mask the subnet boundaries are multiples of 32, so 192.168.5.192 is the network address and 192.168.5.223 is the broadcast address. The address 200 falls in the valid host range 193 through 222, so it is not the network address, meaning the stated failure must be explained by a different configuration issue.

Question 25Network Fundamentals and Models

Which statement accurately compares the behavior of a Layer 2 switch and a router when forwarding a frame between two hosts in different VLANs?

  1. The switch must send the frame to a router or Layer 3 switch to reach the other VLAN Correct answer.
  2. The switch rewrites the destination MAC to the router and forwards it directly
  3. The router forwards the frame using the original destination MAC address
  4. The switch forwards the frame unchanged because VLAN tags are ignored

Explanation

A Layer 2 switch keeps VLANs isolated, so traffic between VLANs must be routed by a router or a Layer 3 switch with interfaces in both VLANs. As the frame leaves the host, the destination MAC is already the gateway's MAC, and the router builds a new frame for the destination VLAN.

Question 26Network Fundamentals and Models

Which OSI layer is responsible for logical addressing and path selection between different networks?

  1. Layer 1, the physical layer
  2. Layer 4, the transport layer
  3. Layer 2, the data link layer
  4. Layer 3, the network layer Correct answer.

Explanation

The network layer handles logical addressing such as IP and decides how packets are routed toward remote networks. The data link layer uses physical MAC addressing inside one link, the transport layer provides end-to-end delivery, and the physical layer moves bits on the medium.

Question 27Network Fundamentals and Models

A frame arrives at a switch port carrying the destination MAC address 01:00:5E:00:00:FB. How does the switch treat this frame?

  1. It rewrites the destination MAC address before forwarding
  2. It forwards the frame only to the port of the default gateway
  3. It drops the frame because the address is not in its MAC table
  4. It floods the frame out all ports in the same VLAN except the ingress port Correct answer.

Explanation

The address 01:00:5E prefix is an IPv4 multicast mapping, and a switch treats a multicast destination as unknown-group traffic. It floods such frames within the VLAN, excluding the port they arrived on, because no single destination port is recorded.

Question 28Network Fundamentals and Models

Which statement describes the role of ARP in the TCP/IP model?

  1. It maps a known IPv4 address to the MAC address needed to build a frame on the local link Correct answer.
  2. It assigns IPv4 addresses to hosts automatically from a configured pool
  3. It translates private IPv4 addresses into public addresses at the network edge
  4. It maps a host name to an IPv4 address before a connection is opened

Explanation

ARP operates between the network and link layers to discover the hardware address that corresponds to an IPv4 address on the same broadcast domain. The resolved MAC address is then used as the frame destination so the packet can be delivered locally.

Question 29Network Fundamentals and Models

A packet with destination 10.50.7.200 arrives at a router whose routing table contains 10.50.0.0/16, 10.50.7.0/24, and a default route. Which entry does the router use to forward the packet?

  1. The 10.50.0.0/16 entry
  2. The default route
  3. The entry with the lowest administrative distance
  4. The 10.50.7.0/24 entry Correct answer.

Explanation

When several routes match a destination, the router prefers the longest prefix match, meaning the most specific network. The /24 covers 10.50.7.200 and is longer than the /16, so it wins regardless of the default route.

Question 30Network Fundamentals and Models

Which statement best explains why the TCP/IP model is described as having four layers while the OSI reference model has seven?

  1. The TCP/IP model is a vendor-specific variant of OSI that renumbers the same seven layers
  2. The TCP/IP model omits the transport layer because TCP and UDP operate at the network layer
  3. The TCP/IP model adds extra layers for encryption and compression that OSI does not define
  4. The TCP/IP model merges the OSI session, presentation, and application functions into one application layer and combines the data link and physical layers into a network access layer Correct answer.

Explanation

The TCP/IP model groups functions by the protocols that implement them, so the top three OSI layers collapse into a single application layer and the bottom two form the network access layer. This mapping preserves the same functional coverage while using fewer, coarser layers.

Question 31IP Addressing, Subnetting, and Routing Basics

Which IPv4 address belongs to the private range defined in RFC 1918 for the 172.16.0.0 block?

  1. 172.16.0.0
  2. 172.16.5.10 Correct answer.
  3. 172.32.0.1
  4. 172.15.255.254

Explanation

RFC 1918 reserves 172.16.0.0 through 172.31.255.255 for private use, so 172.16.5.10 falls inside that block. Addresses below 172.16 or at or above 172.32 are public, and the network address itself cannot be assigned to a host.

Question 32IP Addressing, Subnetting, and Routing Basics

A host is configured with IP address 192.168.10.77 and subnet mask 255.255.255.192. What is the network address of the subnet this host belongs to?

  1. 192.168.10.64 Correct answer.
  2. 192.168.10.32
  3. 192.168.10.0
  4. 192.168.10.128

Explanation

A /26 mask (255.255.255.192) creates blocks of 64 addresses, so the subnet boundaries in the last octet are 0, 64, 128, and 192. The host value 77 falls in the 64–127 block, making 192.168.10.64 the network address.

Question 33IP Addressing, Subnetting, and Routing Basics

How many usable host addresses does a subnet with prefix /27 provide?

  1. 62
  2. 14
  3. 30 Correct answer.
  4. 32

Explanation

A /27 leaves 5 host bits, giving 2^5 = 32 total addresses. Subtracting the network and broadcast addresses leaves 30 usable host addresses.

Question 34IP Addressing, Subnetting, and Routing Basics

Which address is the limited broadcast address used to reach all hosts on the local network segment?

  1. 0.0.0.0
  2. 127.0.0.1
  3. 224.0.0.1
  4. 255.255.255.255 Correct answer.

Explanation

The all-ones address 255.255.255.255 is the limited broadcast address and is never forwarded by routers. It reaches every host on the local segment only.

Question 35IP Addressing, Subnetting, and Routing Basics

A router receives a packet destined for 10.50.7.9. Its routing table contains 10.0.0.0/8, 10.50.0.0/16, and 10.50.7.0/24. Which entry does the router select?

  1. 10.50.7.0/24 Correct answer.
  2. The default route
  3. 10.50.0.0/16
  4. 10.0.0.0/8

Explanation

All three prefixes match the destination, so the router applies the longest-prefix-match rule. The /24 entry is the most specific match and therefore wins.

Question 36IP Addressing, Subnetting, and Routing Basics

What is the primary purpose of the default gateway configured on a host?

  1. To filter inbound traffic by port number
  2. To forward traffic destined for other networks Correct answer.
  3. To assign IP addresses automatically
  4. To resolve hostnames to IP addresses

Explanation

The default gateway is the router address a host uses when the destination is not on its own subnet. The host sends such packets to the gateway, which then routes them onward.

Question 37IP Addressing, Subnetting, and Routing Basics

Which prefix length is equivalent to the subnet mask 255.255.240.0?

  1. /21
  2. /24
  3. /22
  4. /20 Correct answer.

Explanation

The mask 255.255.240.0 has 16 bits set in the first two octets and 4 bits set in the third octet (240 = 11110000), for a total of 20 network bits. It is therefore written as /20.

Question 38IP Addressing, Subnetting, and Routing Basics

A network engineer must divide 192.168.5.0/24 into subnets that each support at least 50 usable hosts. What is the largest prefix length that satisfies this requirement?

  1. /25
  2. /27
  3. /26 Correct answer.
  4. /28

Explanation

A /26 leaves 6 host bits, yielding 64 addresses and 62 usable hosts, which meets the 50-host requirement. A /27 provides only 30 usable hosts, which is too few.

Question 39IP Addressing, Subnetting, and Routing Basics

Which destination address does a host use when it sends an ARP request for another host on the same subnet?

  1. The MAC address of the default gateway
  2. The broadcast MAC address FF:FF:FF:FF:FF:FF Correct answer.
  3. The unicast MAC address of the target host
  4. The multicast MAC address 01:00:5E:00:00:01

Explanation

ARP requests are flooded to the entire broadcast domain, so the frame uses the broadcast MAC address FF:FF:FF:FF:FF:FF. The target replies with a unicast ARP response containing its MAC address.

Question 40IP Addressing, Subnetting, and Routing Basics

A host has address 10.1.2.130 with mask 255.255.255.128. Which address is the directed broadcast address of its subnet?

  1. 10.1.2.191
  2. 10.1.2.129
  3. 10.1.2.255 Correct answer.
  4. 10.1.2.127

Explanation

A /25 mask splits the last octet into blocks of 128, so the subnets are 0–127 and 128–255. Host 130 lies in the second block, whose broadcast address is the all-ones host portion, 10.1.2.255.

Question 41IP Addressing, Subnetting, and Routing Basics

Which statement about the loopback address range 127.0.0.0/8 is accurate?

  1. It identifies all hosts on the local segment.
  2. It is assigned to the first physical interface during boot.
  3. It is routable across the internet as a public range.
  4. Packets sent to it are processed locally and never leave the host. Correct answer.

Explanation

The 127.0.0.0/8 range is reserved for loopback, and traffic sent to it is handled internally by the host's IP stack without reaching a network interface. It is not routable and is not assigned to physical interfaces.

Question 42IP Addressing, Subnetting, and Routing Basics

A router's routing table has no entry matching a packet's destination and no default route is configured. What does the router do with the packet?

  1. It sends the packet back to the source with an ICMP unreachable message. Correct answer.
  2. It forwards the packet to the lowest-numbered interface.
  3. It floods the packet out every interface.
  4. It holds the packet until a matching route appears.

Explanation

When no route matches and no default route exists, the router cannot forward the packet and discards it. It typically returns an ICMP destination-unreachable (network unreachable) message to the sender.

Question 43IP Addressing, Subnetting, and Routing Basics

Which address block is reserved for link-local addressing in IPv4 and is automatically assigned when DHCP fails?

  1. 100.64.0.0/10
  2. 10.0.0.0/8
  3. 169.254.0.0/16 Correct answer.
  4. 192.168.0.0/16

Explanation

The 169.254.0.0/16 range is the IPv4 link-local block used by APIPA when a host cannot obtain a DHCP lease. Hosts on the same segment can still communicate using these addresses.

Question 44IP Addressing, Subnetting, and Routing Basics

A company is assigned 200.1.1.0/24 and needs four subnets of equal size. Which subnet mask should be applied?

  1. 255.255.255.192 Correct answer.
  2. 255.255.255.128
  3. 255.255.255.224
  4. 255.255.255.240

Explanation

Creating four equal subnets requires borrowing 2 host bits, which yields 2^2 = 4 subnets. Adding 2 to the /24 prefix gives /26, whose mask is 255.255.255.192.

Question 45IP Addressing, Subnetting, and Routing Basics

Two hosts, 192.168.1.10/24 and 192.168.2.20/24, are connected to the same layer 2 switch with no router present. What happens when the first host pings the second?

  1. The ping succeeds because both use private addresses.
  2. The ping succeeds only if ARP is disabled.
  3. The ping succeeds because they share a switch.
  4. The ping fails because the hosts are on different subnets. Correct answer.

Explanation

Each host determines that the destination is outside its own /24 subnet and attempts to send traffic to a default gateway. With no router present, the packets cannot be delivered and the ping fails.

Question 46IP Addressing, Subnetting, and Routing Basics

Which routing table entry represents a default route?

  1. 255.255.255.255/32
  2. 127.0.0.0/8
  3. 224.0.0.0/4
  4. 0.0.0.0/0 Correct answer.

Explanation

A default route is written as 0.0.0.0/0, meaning a prefix length of zero that matches every destination. It is used only when no more specific route matches.

Question 47IP Addressing, Subnetting, and Routing Basics

A /29 subnet is required for a small server segment. How many usable host addresses does it contain, and what is the block size in the last octet?

  1. 14 usable hosts with a block size of 16
  2. 6 usable hosts with a block size of 16
  3. 8 usable hosts with a block size of 8
  4. 6 usable hosts with a block size of 8 Correct answer.

Explanation

A /29 leaves 3 host bits, giving 2^3 = 8 total addresses per block and 8 - 2 = 6 usable hosts. The block size in the last octet is therefore 8.

Question 48IP Addressing, Subnetting, and Routing Basics

Which statement correctly describes the difference between a static route and a dynamic route?

  1. A dynamic route never changes once installed.
  2. A static route is learned automatically from neighbors.
  3. A static route is manually configured, while a dynamic route is learned through a routing protocol. Correct answer.
  4. A static route always takes precedence over a more specific dynamic route.

Explanation

Static routes are entered manually by an administrator and do not adapt to topology changes on their own. Dynamic routes are learned and updated by routing protocols such as OSPF or RIP.

Question 49IP Addressing, Subnetting, and Routing Basics

A host with address 172.20.15.200/20 needs to reach a server at 172.20.30.5. What does the host conclude about the destination?

  1. The destination is on the local subnet and is reached directly via ARP.
  2. The destination is a loopback address.
  3. The destination is a broadcast address.
  4. The destination is on a remote subnet and must be sent to the default gateway. Correct answer.

Explanation

A /20 mask covers 172.20.0.0 through 172.20.15.255, so 172.20.30.5 lies outside the host's subnet. The host therefore forwards the packet to its configured default gateway.

Question 50IP Addressing, Subnetting, and Routing Basics

An administrator summarizes four contiguous /24 networks, 10.8.0.0/24 through 10.8.3.0/24, into a single route. Which summary prefix is correct?

  1. 10.8.0.0/21
  2. 10.8.0.0/24
  3. 10.8.0.0/23
  4. 10.8.0.0/22 Correct answer.

Explanation

The four /24 networks span 10.8.0.0 to 10.8.3.255, a range of 1,024 addresses that aligns on a /22 boundary. Combining four /24s removes two bits, giving a /22 summary.