Intro to Networking - Module 2

DHCP (Dynamic Host Configuration Protocol)

A network service that provides automatic assignment of IP addresses and other TCP /IP configuration information. Typically located inside your router or modem. Allows you to set the time limit on assigned IPs, the default gateway IP, and the primary + secondary DNS servers.

Gateway

A node that handles communication between its LAN and other networks. May be a computer, a router, a firewall, or something else.

Registered Ports

1024 - 49151. These ports typically accompany non-system applications associated with vendors and developers.

Root DNS Server

13 servers containing addresses of all DNS servers that contain the master listings for an entire top-level domain

What decimal number corresponds to the binary number 1111 1111?

255, the largest possible number in IPv4.

Suppose you send data to the 11111111 11111111 11111111 11111111 IP address on an IPv4 network. To which device(s) are you transmitting?

255.255.255.255 is reserved for broadcast messages, so all devices on your local network.

DHCPv6 server

A DHCP server that serves up IPv6 addresses. Mostly used to cook up static IP addresses for things like a web server or a DNS server, as IPv6 is usually self-reliant enough to not need it.

NS (Name Server) Record

A DNS lookup file that indicates the authoritative name server for a domain. It's mostly used for delegating subdomains to other name servers.

Recursive Lookup

A DNS query that demands a resolution or the response that the information can't be found.

Iterative Lookup

A DNS query that does not demand a resolution, which means the server provides the information only if it already has that information available.

Forward Lookup

A DNS query that provides an FQDN and requests an IP address.

Reverse Lookup (rDNS)

A DNS query that provides an IP address and requests an FQDN.

Syslog

A Linux or UNIX standard for generating, storing, and processing messages about events on a system. It describes methods for detecting and reporting events and specifies the format and contents of messages. The syslog does not alert a user to problems—it only keeps a history of messages issued by the system.

TTL (Time to Live)

A field that indicates the maximum duration that an IPv4 packet can remain on the network before it is discarded or considered invalid.

PAT (Port Address Translation)

A form of address translation used in private networks that assigns a separate TCP port to each ongoing session between a computer with a private IP and the internet, allowing the gateway to remember which incoming message goes where. A subdivision of a NAT.

Socket

A logical address consisting of a host's IP address combined with the port of an application running on the host, with a colon separating the two values. Example: If a host has an IP address of 10.43.3.87, the socket for Telnet running on that host is 10.43.3.87:23.

Subnet

A logical segment of a larger network, created by an administrator to make network performance more efficient. Requires calculations of IP address ranges within a larger IP address range.

RS (router solicitation)

A message from a client to a router requesting network configuration information.

RA (router advertisement)

A message from a router in response to a client's solicitation, providing DHCP information.

Dual Stacked Network

A network configured to use both IPv4 and IPv6 protocols.

Port

A number assigned to a process, such as an application or a service, that can receive data. Whereas an IP address is used to find a computer, a port is used to find a process running on that computer. TCP and UDP.

DNS Zone

A portion of the DNS namespace for which one organization is assigned authority to manage their own domains. May have one zone, or multiple to make them easier to manage.

IP Exclusion Range

A range of IP addresses within a defined DHCP scope that are excluded from the pool because they're reserved for other devices.

SOA (start of authority) record

A record in a DNS zone listing info about that zone and the records within it. Listed first in a zone file.

Dynamic IP

An IP address that is assigned to a device upon request and may change when the DHCP lease expires or is terminated. Harder to hack.

Static IP

An IP address that is manually assigned to a device and remains constant until it is manually changed. More stable for hosting.

IP Reservation

An IP address that is set aside by a DHCP server for a specific network client, which is identified by its MAC address. Also called MAC reservation or DHCP reservation. Static IP is client-side, while IP Reservation is controlled by the DHCP.

Classful Addressing

An IP addressing convention that adheres to network class distinctions, in which the first 8 bits of a Class A address, the first 16 bits of a Class B address, and the first 24 bits of a Class C address are used for network information.

Classless Addressing

An IP addressing convention that alters the rules of classful IPv4 addressing to create subnets in a network.

URL (uniform resource locator)

An application layer addressing scheme that identifies where to find a particular resource on a network or across networks.

DKIM (DomainKeys Identified Mail)

An authentication method that uses encryption to verify the domain name of an email's sender.

Forwarding DNS Server

An optional server that receives queries from local clients, but doesn't work to resolve the queries. If it has the answer to a query from a prior request, it sends it. If not, it logs the query and passes it on. Used to reduce network traffic on slow links.

How Subnet Masks Identify Host Class

Class A - 255.0.0.0 Class B - 255.255.0.0 Class C - 255.255.255.0

MAC Address

Embedded in every NIC, assumed to be unique. Nodes on a LAN find each other using this. Switches use MAC addresses to determine where to send messages. Data link layer.

When your computer first joins an IPv6 LAN, what is the prefix of the IPv6 address the computer first configures for itself?

FE80::/64

Unicast Address (IPv6)

Generally, any address in networking that represents a single device or interface, instead of a group of addresses (as would be represented by a multicast or broadcast address).

CNAME (Canon Name) Record

Holds alternative names for a host, such as blog.mycompany.com or shop.mycompany.com. These names can be used in place of the canonical name, which is the complete and properly formatted name, such as www.mycompany.com.

TXT Record

Holds any type of free-form text. It might contain text designed to be read by humans regarding network, server, or accounting issues.

AAAA Record

Holds the name-to-address mapping for IPv6 addresses.

What protocol does ping use?

ICMP

MX (Mail Exchange) Record

Identifies an email server and is used for email traffic.

Anycast Address (IPv6)

Identifies multiple destinations, with packets delivered to the closest destination. For example, a DNS server might send a DNS request to a group of DNS servers that have all been assigned the same anycast address. A router handling the request examines routes to all the DNS servers in the group and routes the request to the closest server.

SRV (Service) Record

Identifies the hostname and port of a computer that hosts a specific network service besides email, such as FTP or SIP.

SNAT

sing SNAT (Source Network Address Translation), the gateway assigns the same public IP address to a host each time it makes a request to access the Internet. Small home networks with only a single public IP address provided by its ISP use SNAT.

TFTP (Trivial File Transfer Protocol)

Most commonly used by computers (without user intervention) as they are booting up to request configuration files from another computer on the local network. TFTP uses UDP, whereas normal FTP uses TCP.

Dynamic Port

Number assigned by a client or server as the need arises. For example, if a client application has several open sockets with multiple servers, it can use a different dynamic port number for each socket. 49152-65535.

Private Port

Number assigned by a network administrator that is different from the well-known port number for that service. May be used to test services in private. 49152-65535.

IPv6

The Internet Protocol version 6 is used to provide a large number of new addresses to route Internet traffic, using "from" and "to" addresses written as colon-hexadecimal notation, such as "fe80::42:acff:feaa:1bf0".

fully qualified domain name (FQDN)

The complete domain name of an Internet computer, such as www.website.com.

What type of device does a computer turn to when attempting to connect with a host with a known IP address on another network?

The default gateway is the first device that computers turn to for access to the outside world.

Resource Records

The element of a DNS database stored on a name server that contains information about TCP/IP host names and their addresses.

OUI (Organizationally Unique Identifier)

The first 24 digits of a MAC address, representing the unique code identifying a NIC's manufacturer.

Interface ID

The last 64 bits, or four blocks, of an IPv6 address that uniquely identify the network interface (NIC) on the local link.

TLD (top-level domain)

The last part of an FQDN and the highest-level category used to distinguish domain names—for example, .org, .com, and .net. A TLD is also known as the domain suffix.

DHCP Scope/Pool

The predefined range of addresses that can be leased to any network device on a particular segment.

SLAAC (stateless address autoconfiguration)

The process by which an IPv6 client collects the basic information required to configure its own IPv6 address on a network using a MAC address, without the aid of a DHCPv6 server.

Name Resolution

The process of discovering the IP address of a host when the FQDN is known.

Tunneling

The process of encapsulating one type of protocol in another. For example, transporting IPv6 packets over an IPv4 network.

Which command disables a computer's connection to the network?

ipconfig /release, which releases the dynamic IP given to it until it's given a new one

Class B

Medium Business. 128.0.0.0-191.255.255.255

Which of these commands has no parameters in Windows?

hostname

Well-Known Ports

0-1023 Preassigned for use by common or well known services.

What order does DNS resolution take?

1. Local DNS 2. Root DNS 3. TLD DNS 4. Authoritative DNS

APIPA (Automatic Private IP Addressing)

A service available on Windows that automatically assigns an IP address to a computer configured to search for DHCP when it's on a private IP network and can't reach a DHCP server. Used with IPv4. Most addresses starting with 169.254 are APIPA.

CIDR Notation

A shorthand for expressing an IPv4 address and subnet mask with the IP address followed by a / slash and the number of bits in the IP address that identifies the network. For example, 15.50.35.10/20. Also called slash notation.

NTP (Network Time Protocol)

A simple application layer protocol in the TCP/IP suite used to synchronize the clocks of computers on a network using UTC. NTP depends on UDP for transport layer services.

When is a Socket open and closed?

A socket is open when a session is occurring, allowing an ongoing conversation between two hosts. When this session ends, the socket is closed.

IPAM (IP address management)

A standalone product or application embedded in another product, such as Windows Server, that provides a way to plan, deploy, and monitor a network's IP address space.

LDAP (Lightweight Directory Access Protocol)

A standard protocol for accessing network directories. Uses SSL to encrypt.

NAT (Network Address Translation)

A technique in which IP addresses used on a private network are assigned a shared public IP address by a gateway when accessing a public network.

Caching DNS Server

A temporary database on a client machine that accesses public DNS data and caches the recent DNS information it collects. This server receives DNS queries first, and works to resolve them by contacting external DNS servers for information, or by providing recent cached information.

PTR (Pointer) Record

A type of DNS data record that is used for reverse lookups, to provide a host name when the IP address is known.

Address Record

A type of DNS data record that maps the IPv4 address of an Internet-connected device to its domain name.

Multicast Address (IPv6)

A type of IPv6 address that represents multiple interfaces, often on multiple nodes, used to send a packet to a targeted group of nodes.

SPF (Sender Policy Framework)

A validation system that helps fight spam by identifying the email servers allowed to send email on behalf of a domain.

Loopback Address

An IP address that indicates your own computer and is used to test TCP/IP configuration on the computer.

DNS Messages

Application layer messages that use UDP at the transport layer. Communication with DNS servers occur through port 53.

IP Address

Assigned to a network connection made by a node. Routers use IP addresses to determine which network to send a message to. Network layer.

What does IPv6 eliminate from IPv4?

Broadcasting. Messages are no longer sent to every node on a network, as broadcasting has been replaced by Anycast.

Global Address (IPv6)

Can be routed on the Internet and is similar to public IPv4 addresses. Most begin with the prefix 2000::/3.

BIND

DNS Server Software for Windows/Linux/Unix.

DNS Server (Windows)

DNS Server Software on Windows Server.

Subnet Mask

In IPv4 addressing, a 32-bit number that, when combined with a device's IP address, indicates what kind of subnet the device belongs to.

Default Gateway

In a TCP/IP network, the nearest/default gateway to a particular host. This router's IP address is part of the necessary TCP/IP configuration for communicating with multiple networks using IP.

Class A

Large Business. 1.0.0.0 - 127.255.255.255

SQLnet

Oracle Net Services. Used by Oracle Database to communicate with other Oracle Databases or with database clients. This interconnection allows applications and databases to be distributed across different machines and still communicate as if they were on the same machine.

Which DNS server offers the most current resolution to a DNS query?

Primary.

RFC1918 Addresses

Private, inward-facing IP addresses.

Broadcast Message

Received and processed by all computers on the same LAN. Uses the IP 255.255.255.255.

Class C

Small Business and Home Use. 192.0.0.0-223.255.255.255

Link (IPv6)

Sometimes called a local link. Any LAN bounded by routers.

You have just brought online a new secondary DNS server and notice your network-monitoring software reports a significant increase in network traffic. Which two hosts on your network are likely to be causing the increased traffic and why?

The secondary and primary DNS servers because the secondary server is requesting zone transfers from the primary server

Domain Name

The unique domain used as a stand-in for an IP address. For example: www.[website].com, where the [website] is the Domain Name.

Host Name

The unique name a host on a network is assigned, for example: [www.]website.com, where the www is the Host Name.

Namespace Databases

Thousands of servers across the world, each providing DNS services. Each organization offering host services is responsible for providing and maintaining its own DNS authoritative servers, or using a third-party DNS server.

Multicast Flooding (IPv6)

Traffic congestion on a network caused by a weakness in the way switches learn MAC addresses of network devices, causing it to assign an IP address to a multicast group. To fix this, IGMP snooping must be enabled on a switch, allowing it to direct multicast traffic.

Neighbors (IPv6)

Two or more nodes on the same link (LAN).

SMB (Server Message Block)

Used by earlier Windows OSs for file sharing on a network. UNIX uses a version of SMB in its Samba software, which can share files with other operating systems, including Windows systems.

Link Local Address (IPv6)

Used for communicating with nodes in the same link and is similar to an autoconfigured APIPA address in IPv4. It begins with FE80::/10. Not allowed to go beyond the local link.

DNAT

Using DNAT (Destination Network Address Translation), hosts outside the network address a computer inside the network (such as a web server or an email server) by a predefined public IP address. When a message sent to the public IP address reaches the router managing DNAT, the destination IP address is changed to the private IP address of the host inside the network. The router must maintain a translation table of public IP addresses mapped to various hosts inside the network.