1. Unicast — A transmission refers to one advice sending a message to one other device in one-to-one communications. A unicast packet has a destination IP address that is a unicast address which goes to a single recipient. A source IP address can only be a unicast address, because the packet can only originate from a single source. Range 1.1.1.1 to 223.225.255.255.
  2. Broadcast — Broadcast transmission refers to a device sending a message to all the devices on a network in one-to-all communications. A broadcast packet has a destination IP address with all ones(1s) in the host portion, or 32 one(1)bits. However there are no broadcast packets with IPv6. A broadcast packet must be processed by all devices in the same broadcast domain. A broadcast domain identifies all hosts on the same network segment. A broadcast may be directed or limited. A directed broadcast is sent to all hosts on a specific network.
  3. Multicast — Multicast transmission reduces traffic by allowing a host to send a single packet to a selected set of hosts that subscribe to multicast group. A multicast packet is a packet with a destination IP address that is a multicast address. IPv4 has reserved the 224.0.0.0 to 239.255.255.255 addresses as a multicast range. Hosts that receive particular multicast packets are called multicast clients. The multicast clients use services requested by a client program to subscribe to the multicast group. Each multicast group is represented by a single IPv4 multicast destination address.
  4. Types of IPv4 addresses → Public and Private IPv4 addresses — Public IPv4 addresses are addresses which are globally routed between internet service provider(ISP) routers. However, not all available IPv4 addresses can be used on the internet. There are blocks of addresses called private addresses that are used by most organizations to assign IPv4 addresses are not unique and can be used. →Private IPv4 Addresses and Network Address Translation(NAT) — — Before the ISP can forward this packet, it must translate the source IPv4 address, which is a private address, to a public IPv4 address using Network Address Translation (NAT). NAT is used to translate between private IPv4 and public IPv4 addresses. This is usually done on the router that connects the internal network to the ISP network. Private IPv4 addresses in the organization's intranet will be translated to public IPv4 addresses before routing to the internet. →Activity-Pass or Block IPv4 Addresses — decide to Pass or Block each IP address depending on whether it is Public (the internet) or Private (small local network). Click Start to begin and click on either Pass or Block.
  5. Special Use IPv4 Addresses There are certain addresses, such as network address and broadcast address, that cannot be assigned to hosts. There are also special addresses that can be assigned to hosts, but with restrictions on how those hosts can interact within the network. Loopback addresses ARE commonly identified as only 27.0.0.1. These are special addresses used by a host to direct traffic to itself. Link-Local addresses are more commonly known as the Automatic Private IP Addressing or Self-assigned addresses. They are used by a Windows client to self-configure in the event that the client cannot obtain an IP addressing through other methods. Link-local addresses can be used in a peer-to-peer connection but are not commonly used for this purpose.
  6. Legacy Classful Addressing — In 1981, IPv4 addresses were assigned using classful addressing as defined in RFC 790, Assigned numbers. Customers were allocated a network address based on one of three classes, A, B, or C. The RFC divided the unicast ranges into specific classes as follows: → Class A (0.0.0.0/8 — 127.0.0/8)- Designed to support extremely large networks with more than 16 million host addresses. → Class B(128.0.0.0/16–191.255.0.0/16)- Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses. →Class C(192.0.0.0/24–223.255.255.0/24)- Designed to support small networks with a maximum of 254 hosts. Note — There is also a Class D multicast block consisting of 224.0.0.0 and a Class E experimental address block consisting of 240.0.0..-225.0.0.0.
  7. Assignment of IP addresses →Regional Internet Registries — Public IPv4 addresses are addresses which are globally routed over the internet. Public IPv4 addresses must be unique. Both IPv4 and IPv6 addresses are managed by the Internet Assigned Numbers Authority(IANA). The IANA manages and allocates blocks of IP addresses to the Regional Internet Registries(RIRs). The five RIRs are shown in the figure. RIRs are responsible for allocating IP addresses to ISPs who provide IPv4 address blocks to organizations and smaller ISP s. Organization can also get their addresses directly from an RIR.
  8. "Private IPv4 addresses are assigned to devices within an organization's intranet(internal network) and any organizations(home, school, office, company) can use the 10.0.0.0/8 address."
  9. "To access a device over the internet, the destination IPv4 address must be a public address. Public IPv4 address exhaustion is a reason why there are private IPv4 address and why organizations are transitioning to IPv6."
  10. "RIRs receive IP addresses from IANA and are responsible for allocating these addresses to ISPs and some other organizations."
  11. Broadcast Domains and Segmentation → Routers segment Broadcast Domain — In an Ethernet LAN, devices use broadcasts and the Address Resolution Protocol(ARP) to locate other devices. ARP sends layer 2 broadcast to a known IPv4 address on the local network to discover the associated MAC address. Devices on Ethernet LANs also locate other devices using services.
  12. Problems with Large Broadcast Domains → A large Broadcast Domain — A large broadcast domain is a network that connects many hosts. A problem with a large broadcast domain is that these hosts can generate excessive broadcasts and negatively affect the network. →Communicating Between Networks — The solutions is to reduce the size of the network to create smaller broadcast domains in a process called subnetting. These smaller networks spaces are called subnets.
  13. Reasons for Segmenting Networks Subnetting reduces overall network traffic and improves network performance. It also enables an administrator to implement security policies such as which subnets are allowed or not allowed to communicate together. Another reason is that it reduces the number of devices affected y abnormal broadcast traffic due to misconfigurations, hardware/software problems, or malicious intent. There are various ways of using subnets to help manage network devices: → Subnetting by location → Subnetting by Group or Function → Subnetting by Device type
  14. "Routers will not forward an IPv4 broadcast packet by default."
  15. "Slow network operations and slow device operations are the result of excessive broadcast traffic."