9 - IPv4 and Network Segmentation
9.0.2 What will I learn in this module ?
| IPv4 Unicast, Broadcast, and Multicast | Compare the characteristics and uses of the unicast, broadcast and multicast IPv4 addresses. |
| Types of IPv4 addresses | Explainn public, private, and reserved IPv4 addresses. |
| Network segmentation | Explain how subnetting segments a network to enable better communication. |
9.1.2 Unicast
Unicast transmission refers to one device 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. This is regardless of whether the destination IP address is a unicast, broadcast, or multicast.
IPv4 unicast host addresses are in the address range of 1.1.1.1 to 223.255.255.255. However, within this range are many addresses that are reserved for special purposes.
9.1.4 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.
Note: IPv4 uses broadcast packets. 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. For example, a host on the 172.16.4.0/24 network sends a packet to 172.16.4.255. A limited broadcast is sent to 255.255.255.255. By default, routers do not forward broadcasts.
Broadcast packets use resources on the network and make every receiving host on the network process the packet. Therefore, broadcast traffic should be limited so that it does not adversely affect the performance of the network or devices
9.1.6 Multicast.
Multicast transmission reduces traffic by allowing a host to send a single packet to a selected set of hosts that subscribe to a 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. When an IPv4 host subscribes to a multicast group, the host processes packets addressed to this multicast address, and packets addressed to its uniquely allocated unicast address.
Routing protocols such as OSPF (Open Shortest Path First) use multicast transmissions. For example, routers enabled with OSPF communicate with each other using the reserved OSPF multicast address 224.0.0.5. Only devices enabled with OSPF will process these packets with 224.0.0.5 as the destination IPv4 address. All other devices will ignore these packets.