Computer Networks Quiz

A network is a collection of two or more devices that can communicate with each other.

A Local Area Network (LAN) is a network that connects devices within a small geographical area, like a home or office.

A Wide Area Network (WAN) connects devices over a large geographical area, spanning cities, countries, or even the world.

A Metropolitan Area Network (MAN) connects devices within a city or town, usually covering a larger area than a LAN but smaller than a WAN.

Network communication refers to the exchange of data between two or more connected devices on a network.

Simplex communication is a one-way transmission of data, where information flows in only one direction.

Half-duplex communication allows data to flow in both directions, but only one device can transmit at a time.

Full-duplex communication allows data to flow in both directions simultaneously, enabling two-way conversations.

The Application Layer is where end users interact with software applications. This is the top layer of the OSI model and is responsible for providing services to users.

The Presentation Layer handles data formatting, encryption, and compression to ensure data is transmitted in a standard way that both the sending and receiving systems understand.

The Session Layer manages communication sessions between devices, handling tasks like authentication and reconnection.

The Transport Layer is responsible for segmenting and reassembling data from upper-layer applications, ensuring data integrity using flow control.

The Network Layer manages device addressing, tracking their locations and routing data between them. Routers function at this layer.

The Data Link Layer manages the physical transmission of bits on a network, ensuring accurate delivery and handling error notification.

The Physical Layer is the lowest layer of the OSI model and deals with the physical transmission of unstructured data bits across the network.

TCP is a connection-oriented protocol. This means that a connection must be established before data can be transferred, ensuring reliable and ordered data transmission.

The TCP Three-Way Handshake is a series of messages exchanged between two devices to establish a reliable connection. This process involves SYN, SYN/ACK, and ACK segments.

The Window Size indicates the number of bytes a sender can send before receiving an acknowledgement from the receiver. This helps manage the flow of data and prevent congestion.

The RST bit is used to reset a TCP connection. It's a flag that signals the destination device to terminate the connection due to an error or a security issue.

TCP Flags guide the flow of data across a TCP connection, indicating functions like data pushing, connection termination, priority, and acknowledgement.

The PUSH flag tells the receiver's application to immediately process the buffered data, ensuring it's sent with priority.

The URG flag designates data as urgent, instructing the receiving station to prioritize it over other data.

Sequence numbers and acknowledgement numbers ensure reliable data delivery in TCP. Sequence numbers track the order of data packets, and acknowledgement numbers confirm their receipt.

A special IP address used when a DHCP server is unavailable, allowing devices to communicate on the local network.

The range of IP addresses used by APIPA, allowing devices to communicate without a DHCP server.

A device that forwards DHCP requests and responses between clients and servers on different subnets.

A DHCP message sent by a client to inform the server that the requested IP address is already in use.

A DHCP message sent by the server to the client when the requested IP address is unavailable or other issues arise.

A hierarchical system that maps human-readable domain names to numerical IP addresses.

The primary function of a DNS server is to translate domain names into IP addresses.

The standard port used by DNS servers for communication over the network.

The process of resolving a domain name (like example.com) into an IP address.

The process of resolving an IP address into a domain name.

A record containing information about a resource on a network, including its name, IP address, and other details.

A section of the DNS namespace managed by a specific DNS server.

The original and authoritative source for a DNS zone's data, allowing for modifications and updates.

A read-only copy of a DNS zone, updated through zone transfers from a primary server.

A DNS zone that only contains information about the authoritative servers for another zone, used for resolving names within that zone efficiently.

An A record maps a fully qualified domain name (FQDN) to an IP address.

A CNAME record creates an alias or a synonymous name for a specific FQDN.

An MX record specifies the mail exchange server associated with a DNS domain.

An NS record indicates the servers that are authoritative for a specific zone.

A PTR record maps an IP address back to its corresponding FQDN.

SRV records enable you to specify the location of servers for specific services, protocols, and domains.

The primary name server is the authoritative source of data about its zone. It's the 'master copy'.

A secondary name server gets its data from the primary name server. It's a backup copy.

A root name server is authoritative for the root domain (the .). It's the top level.

Round robin DNS is used to distribute traffic among multiple servers, ensuring load balancing.

DNS servers use port 53 by default. Incoming and outgoing DNS packets should be allowed through this port.

The three-way handshake is the process by which TCP establishes a reliable connection. It involves a SYN, SYN/ACK, and ACK exchange.

The window size in TCP indicates the number of bytes a sender can send before receiving acknowledgment from the receiver.

The RST bit in TCP is used to reset a connection if it's not allowed or there are errors.

A routing protocol learns routes by exchanging information with neighboring routers using the same protocol.

A protocol that carries data between different networks.

Routes are manually configured on the router by a network administrator.

Routing protocols that use the number of hops as the metric to find the best path to a destination.

Routing protocols that share information about the network topology with all routers.

Hybrid routing combines the benefits of distance-vector and link-state protocols.

A group of networks under a single administrative control.

The trustworthiness of a routing protocol, used to prioritize routes from different protocols.

A value that routing protocols use to determine the best path to a destination network.

The number of routers that data must pass through to reach the destination network.

Network performance metrics used to assess network quality.

The inverse proportion of bandwidth, used in some routing protocols.

A distance-vector routing protocol that uses hop count as the metric to determine the best path.

Time intervals used in RIP to manage routing information.

The main differences between RIP versions.

A flag in the IP header used to indicate that the sender has received packets with sequenced numbers from 0 to 9, and is expecting the next packet to have a sequence number of 10.

It sets the priority of the data transmission, informing the receiver that this information is important.

A TCP flag that initiates a connection and synchronizes the sequence numbers between the communicating parties.

The process of breaking larger IP packets into smaller fragments.

The maximum size of an IP packet that can be transmitted over a specific network interface.

The device that receives and reassembles fragmented IP packets.

The process of reassembling fragmented IP packets by storing them in a buffer based on their fragment offset field.

A flag that prohibits fragmentation of a packet. If set, a router will discard the packet if it needs to be fragmented.

A flag that indicates whether there are more fragments to be received for a particular IP datagram. The last fragment has this flag set to 0, indicating that all fragments have been received.

A field in the IP header that specifies the size of each fragmented packet.

A field that indicates the number of hops an IP packet can travel in the network before being discarded.

A field that identifies the upper-layer protocol to which the IP datagram should be delivered, such as TCP or UDP.

The process of forwarding packets between networks that are not directly connected.

A networking device responsible for routing packets between different networks, operating at Layer 3 of the OSI model.

The various types of memory used by routers for different purposes.

A mechanism in EIGRP that prevents routes learned on one interface from being advertised back out of the same interface, avoiding routing loops.

A special entry in the EIGRP routing table used only for summarization, which terminates any traffic destined for it, preventing it from causing routing loops.

A state in which a router has a successor route for a destination, meaning it has a path to reach it.

A state in which a router has lost its primary path to a destination and is actively searching for alternative routes by sending query packets to its neighbors.

A situation where a router remains in an Active state for an extended period because it cannot find a feasible alternative route to a destination.

A message sent by a router when it is shutting down its EIGRP process, informing its neighbors to recalculate their routes without waiting for the hold timer to expire.

A command that disables EIGRP on a specific interface, preventing the router from forming neighbor relationships and exchanging routing updates through that interface.

A condition used by EIGRP to determine if a route is a feasible successor, requiring the advertised distance of the feasible successor to be less than the feasible distance of the current successor.

The multicast IP address used by EIGRP to communicate with other routers on the network.

An open standard link-state routing protocol that uses the Dijkstra algorithm to calculate shortest paths and populate the routing table with optimal routes.

Dividing an autonomous system into multiple areas can reduce route updates, conserve network resources, and limit the spread of network problems.

A special area in an OSPF network that acts as a central hub for inter-area traffic, where all other areas must connect.

A router connecting other areas to the backbone area in an OSPF network.

A router that connects different Autonomous Systems (AS) in an OSPF network.

A unique identifier used to distinguish an OSPF router, typically derived from the highest IP address of its loopback interfaces or its physical interfaces if no loopback is present.

Split Horizon prevents a route learned on an interface from being advertised back out of the same interface, preventing routing loops.

Route poisoning involves advertising a route with an infinite metric when the route is invalid. In RIP, this typically means a metric of 16.

The passive-interface command on a router can stop RIP updates from propagating out a specific interface, conserving bandwidth.

RIP relies on UDP port number 520 to send routing updates.

RIP has an administrative distance (AD) of 120, indicating its priority in routing decisions. Lower AD scores have higher priority.

RIP uses the multicast address 224.0.0.9 to send routing updates to other RIP-enabled devices.

EIGRP is a sophisticated routing protocol that uses a combination of distance-vector and link-state elements.

EIGRP uses a 'diffused update algorithm' (DUAL) to calculate the shortest path, making it more efficient than basic distance-vector protocols.

For EIGRP routers to become neighbors, the 'hello' packets they exchange must match on these parameters: Autonomous System number, K-values, Authentication, primary address, and static neighborship if applicable.

EIGRP considers bandwidth (K1) and delay (K3) by default when calculating the routing metric. Other parameters like load, reliability, and MTU can be configured (K2, K4, K5).

The EIGRP metric formula calculates a cost based on the lowest bandwidth link and the cumulative delay of the path. The formula is 256 * [(10^7 / lowest-bandwidth) + cumulative-delay].

EIGRP uses the Protocol Dependent Module (PDM), Reliable Transport Protocol (RTP), Neighbor Discovery and Recovery Module, and Diffusing Update Algorithm (DUAL) for its functionality.

EIGRP uses hello, acknowledgement, update, query, and reply packets to communicate between routers.

RTP (Reliable Transport Protocol) is used by EIGRP to ensure the reliable and ordered delivery of packets between routers.

Update, Query, and Reply packets in EIGRP use RTP to ensure their reliable delivery.

If an EIGRP packet is not acknowledged, the router will resend it as a unicast to the non-responding neighbor. After 16 failed retransmissions, the neighbor is removed from the table.

A device that connects multiple devices within a Local Area Network (LAN) and forwards data packets based on destination MAC addresses.

The process of forwarding data packets between devices on the same network by examining destination MAC addresses.

A device that connects multiple devices on a network, but simply broadcasts data to all ports without analyzing packet destinations.

A mechanism to divide a single physical interface on a router into multiple logical interfaces, each associated with a specific VLAN.

A group of devices that can receive broadcast packets originating from any device within the network segment.

A network segment where devices can potentially interfere with each other's transmissions leading to collisions.

A table maintained by a switch to store MAC addresses of connected devices along with their corresponding ports.

When a frame reaches the switch, it examines the source MAC address and adds it to the MAC address table with the incoming port, allowing it to learn the location of devices.

A protocol that prevents network loops by blocking redundant paths, ensuring data flows efficiently through a network.

A special type of ICMP message indicating a packet is dropped because the Time-To-Live (TTL) value reached zero, signifying the packet traveled through the maximum allowed hops.

A special UDP port used by Traceroute, which triggers a 'Destination Unreachable' ICMP message indicating the destination has been reached.

Traceroute sends three packets for each TTL value and records the round trip time to each hop.

A network protocol used to test the path taken by data packets from the source to the destination, providing hop information and time measurements.

Each port on a switch creates a separate collision domain, preventing collisions between devices on the same network.

Network Address Translation (NAT) is a technique that translates private IP addresses to public IP addresses. It allows multiple devices on a private network to share a single public IP address, conserving address space and improving security.

Static NAT maps a specific private IP address to a specific public IP address. It's like assigning a permanent phone number to a specific person.

Dynamic NAT maps private IP addresses to public IP addresses from a pool, allowing more flexibility. It's like assigning phone numbers from a pool to different callers.

Port Address Translation (PAT) maps multiple private IP addresses to a single public IP address using different port numbers. It allows many users to connect to the internet using a single public IP address.

Inside local addresses are the private IP addresses of hosts within a private network. Inside global addresses are the public IP addresses assigned to those hosts by NAT.

Outside local addresses are the IP addresses of the router interfaces connected to the ISP. Outside global addresses are the IP addresses of destination hosts on the public internet.

ARP works at the Data Link Layer (Layer 2) of the OSI model because it handles physical addressing and communication.

ARP is used to resolve IP addresses to the corresponding MAC addresses, allowing devices on a network to communicate with each other.

An ARP table (cache) is a table that stores mappings between IP addresses and MAC addresses. It allows devices to quickly find the MAC address corresponding to an IP address.

In an ARP Request packet, the source MAC address is the sender's MAC address and the destination MAC address is FF:FF:FF:FF:FF:FF (broadcast). In an ARP Reply packet, the source is the MAC address of the responding host, and the destination is the MAC address of the host that sent the ARP Request.

Proxy ARP is when a device intercepts an ARP request for another device. It's like someone answering the phone and claiming to be someone else.

Gratuitous ARP is when a device sends an ARP request for itself to broadcast its presence. It's like a device saying, “Hey, I'm here with this IP address.”

Reverse ARP is used to obtain a device's IP address if its MAC address is already known. It's like looking up someone's phone number based on their address.

While BGP routers can be in the same subnet, they don't have to be. They communicate using TCP connections, which can work across different networks.

BGP uses TCP port 179 to establish connections between routers.

Interior BGP (iBGP) is used within the same autonomous system, while Exterior BGP (eBGP) is used between different autonomous systems.

BGP uses an administrative distance (AD) of 20 for iBGP and 200 for eBGP. Lower AD means a route is preferred.

BGP uses two mechanisms to prevent routing loops: 1. A router doesn't advertise routes learned from an iBGP peer to other iBGP peers. 2. It adds its own ASN to the AS_PATH when advertising to an eBGP peer.

A hard reset completely resets the BGP connection, removing all learned entries, while a soft reset just updates the BGP table.

BGP uses different message types for communication: Open (initial connection), Keepalive (heartbeat), Update (routing information), and Notification (error).

BGP goes through different stages when establishing a connection: Idle, Connect, Active, OpenSent, OpenConfirm, and Established.

BGP uses path attributes to determine the best route. These include: Next Hop, Weight, Local Preference, AS Path, Origin, Multi-Exit Discriminator (MED), and more.

BGP Weight is a local preference used by a router to influence its route selection. Higher Weight means a route is preferred.

BGP Local Preference is a value used within an autonomous system to select the best route for reaching a specific network. Higher Local Preference is better.

Next Hop attribute in BGP indicates the IP address of the next router in the path to reach a destination. If the Next Hop is unreachable, the route cannot be used.

AS Path attribute indicates the number of autonomous systems a route has traversed. Routes with shorter AS Paths (fewer systems) are preferred.

Origin attribute in BGP indicates the source of a route. Interior Gateway Protocol (IGP) is preferred over Exterior Gateway Protocol (EGP) routes.

A router with the highest priority becomes the designated router (DR), and the router with the second highest priority becomes the backup designated router (BDR). If there's a tie in priority, the router with the highest router ID wins.

OSPF routers maintain three tables: the neighbor table, which stores information about neighboring routers; the topology table, which maps the network structure; and the routing table, which stores the best paths for routing data.

When two OSPF routers decide to exchange routing information, they send each other a list of all their LSAs (Link-State Advertisements) - essentially their view of the network. Then, each router checks its own database and requests missing LSAs from the neighbor.

OSPF uses the multicast address 224.0.0.5 for general OSPF communication and 224.0.0.6 for multicast routing.

OSPF routers go through several states before establishing a neighbor relationship, from Down (no Hello packets) to Attempt (manual neighbor configuration on non-broadcast networks), Init (received Hello), 2-way (bidirectional Hello), Exstart (DR/BDR adjacencies), Exchange (DBD packets), Loading (LSR/LSU exchange), and finally, Full (database synchronization).

The Hello interval defines how frequently routers send Hello packets, and the dead interval defines how long a router waits for Hello packets before declaring a neighbor dead. The default Hello interval is 10 seconds, and the default dead interval is 40 seconds (four times the Hello interval).

OSPF uses Type 1 LSAs (Router LSAs) to advertise interface information and costs, Type 2 LSAs (Network LSAs) to advertise network information and DRs, Type 3 LSAs (Summary LSAs) to advertise inter-area routes, Type 4 LSAs (Summary ASBR LSAs) to advertise ASBRs, Type 5 LSAs (External LSAs) to advertise external routes, and Type 7 LSAs (Not-So-Stubby Area LSAs) to advertise Type 5 LSAs in a Not So Stubby Area (NSSA).

It's a process that involves three steps: two-way communication using Hello packets, database synchronization (exchanging DBD, LSR, and LSU packets), and finally, achieving adjacency once databases are synchronized. This essentially establishes a neighbor relationship where routers share and propagate routing information.

DR and BDR are elected to optimize OSPF communication. By having all routers connect to the DR and BDR for updates instead of flooding information to all routers directly, it significantly reduces network traffic and conserves bandwidth.

The router ospf <process-id> command enables the OSPF process, where is a unique identifier for the OSPF process. Then, network <network-address> <wildcard-mask> area <area-id> configures a specific network in a particular area.

These are the packets exchanged between OSPF routers during the database synchronization process. DBD (Database Descriptor) packets describe the router's database, LSR (Link-State Request) packets request missing LSAs, and LSU (Link-State Update) packets transmit the requested LSAs.

OSPF routers must have the same subnet, area ID, Hello and Dead interval time, and authentication settings to become neighbors. This ensures they can communicate and exchange routing information efficiently.

OSPF routers are configured to send Hello messages periodically to their neighbors. The Hello interval defines how often these messages are sent. The default Hello interval is 10 seconds.

In OSPF, once a router receives a Hello message from another router, it enters the Init state. This is the initial step towards establishing a neighbor relationship, confirming the neighbor's existence.

An attribute that influences how other Autonomous Systems (AS) choose the best path to reach a specific prefix within your AS. It's communicated only to neighboring AS and prefers routes with lower MED values.

A process where a router performs two lookups to reach a destination: first for the next hop in the remote AS, and then for the route to reach that next hop. This happens when the destination network isn't directly connected.

A BGP device that helps share routes learned from internal BGP (iBGP) neighbors with other iBGP neighbors. It acts as a server, allowing clients to exchange routes without direct connections.

Controls how your own AS chooses the best path to exit and reach another AS. A higher value means a more preferable path. Defaults to 100 and can be adjusted.

A packet filtering mechanism that controls network traffic based on rules defined in a list of criteria. It allows or denies packets based on source/destination addresses, protocol, port, etc.

A type of ACL that focuses only on the source IP address of incoming packets. It can permit or deny access based on the source address only.

A type of ACL that examines more than just the source address. It can filter based on source, destination, protocol, port, and more.

ACLs that can be assigned names like 'CCNA' instead of using just numbers. This improves readability and allows for easier management.

A special notation used with ACLs to specify individual hosts, networks, or ranges. It's the opposite of a subnet mask, with 0s indicating matching and 255s indicating don't care.

A technique that translates private IP addresses into public IP addresses. It allows devices on a private network to connect to the internet.

Rules applied to packets that are entering an interface. They are processed before routing decisions.

Rules applied to packets leaving an interface. They are processed after packets are routed.

A command that provides information about the number of times each rule in an ACL has been matched (hit count).

A command that shows only the configuration of a rule in an ACL, without any hit count information.