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  1. Wikipedia: Internet layer
  2. Wikipedia: Internet Protocol
  3. Wikipedia: IPv4
  4. Wikipedia: IP address
  5. Wikipedia: Classful network


  1. YouTube: An overview of IPv4 and IPv6 - CompTIA Network+ N10-005: 1.3
  2. YouTube: Basics of ipconfig, ping, tracert, nslookup and netstat


  1. Use a Regional Internet Registry to search the Whois database for IP address information.
  2. Review Wireshark: Internet Protocol (IP).
  3. Use Wireshark to capture and analyze local IPv4 traffic.
  4. Use Wireshark to capture and analyze remote IPv4 traffic.
  5. Use Wireshark to capture and analyze fragmented IPv4 traffic.
  6. Consider situations in which a packet analyzer might be used to troubleshoot IPv4 traffic.

Lesson Summary[edit]

  • The Internet layer is a group of internetworking methods, protocols, and specifications in the Internet protocol suite that are used to transport datagrams from the originating host across network boundaries, if necessary, to the destination host specified by a network address.[1]
  • The Internet layer is not responsible for reliable transmission. It provides only an unreliable connection-less service, and "best effort" delivery.[2]
  • The core protocols used in the Internet layer are IPv4, IPv6, the Internet Control Message Protocol (ICMP), and the Internet Group Management Protocol (IGMP).[3]
  • The Internet Control Message Protocol (ICMP) is primarily used for error and diagnostic functions.[4]
  • The Internet Group Management Protocol (IGMP) is used by IPv4 hosts and adjacent multicast routers to establish multicast group memberships.[5]
  • Internet Protocol Security (IPsec) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream.[6]
  • Each IP datagram has two components, a header and a data payload. The IP header is tagged with the source IP address, destination IP address, and other meta-data needed to route and deliver the datagram.[7]
  • IPv4 uses 32-bit (four-byte) addresses, most often written in the dotted decimal notation, which consists of four octets of bit values expressed individually in decimal and separated by periods.[8]
  • Private IPv4 network address ranges are reserved for use in private networks and include, and Private networks communicate with public networks through network address translation (NAT).[9]
  • The link-local IPv4 address range,, is similar to a private network address range but is not routable. These addresses are most often used when a host cannot obtain an IP address from a Dynamic Host Configuration Protocol (DHCP) server.[10]
  • The loopback address range, is reserved for loopback, or internal host addressing.[11]
  • The primary address pool of the Internet, maintained by the Internet Assigned Numbers Authority (IANA), was exhausted on 3 February 2011.[12]
  • Valid IPv4 host addresses have a first octet in the range 1-126 (originally Class A), 128-191 (originally Class B), or 192-223 (originally Class C). Multicast addresses have a first octet in the range 224-239 (originally Class D). Addresses with a first octet in the range 240-255 are unused (reserved / experimental).[13][14]
  • Classful networking was replaced by Classless Inter-Domain Routing (CIDR) starting in 1993.[15] However, the basic addressing concepts developed under classful networking still apply to IPv4. The CIDR changes apply to subnetting and routing, which will be examined in the next lesson.

Key Terms[edit]

American Registry for Internet Numbers (ARIN)
The Regional Internet Registry (RIR) for Canada, many Caribbean and North Atlantic islands, and the United States.[16]
data corruption
Errors in computer data that occur during writing, reading, storage, transmission, or processing, which introduce unintended changes to the original data.[17]
A basic transfer unit associated with a packet-switched network in which the delivery, arrival time, and order of arrival are not guaranteed by the network service.[18]
A network point that acts as an entrance to another network.[19]
A computer connected to a computer network and assigned a network layer host address.[20]
Internet Assigned Numbers Authority (IANA)
The entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Internet Protocol-related symbols and numbers.[21]
Internet Protocol (IP)
The principal communications protocol responsible for addressing hosts and routing datagrams (packets) from a source host to the destination host across one or more networks.[22]
IP fragmentation
The Internet Protocol fragmentation and reassembly procedure that can break a datagram into pieces that may later be reassembled based on identification, offset, and length.[23]
network address translation (NAT)
The process of modifying IP address information in IP packet headers while in transit across a traffic routing device.[24]
A unit of digital information in computing and telecommunications that consists of eight bits.[25]
packet switching
A digital networking communications method that groups all transmitted data into variably-sized blocks, called packets, for delivery over a shared network.[26]
Regional Internet Registry (RIR)
An organization that manages the allocation and registration of Internet number resources within a particular region of the world.[27]
robustness principle
Be liberal in what you accept, and conservative in what you send.[28]
The ability of a system, network, or process, to handle a growing amount of work in a capable manner or its ability to be enlarged to accommodate that growth.[29]

See Also[edit]