Network+ Exam Objectives 1.4

1.4 Given a scenario, evaluate the proper use of the following addressing technologies and addressing schemes:

Networks now compared to networks then are much more complex and even today networks, their uses, and what we want to use them for continues to grow. Nowadays networks are used for a plethora of purposes, from receiving and sending emails, chatting, sending data, and so much more. A network’s security requires knowledge in ports, addressing, and controlling data traffic. It’s important to know how network and addressing technologies should, are, and can be used as well as to know how network traffic should be addressed.

Addressing Technologies

Most networks today use IP addressing but there is more than one type of ways to address using IP. The method used highly depends on the network administrators as well as network needs.

                         

• Subnetting – Subnetting is required in order to create more broadcast domains. With subnetting you are able to reduce a broadcast’s effect on a host because there will be a reduced number of hosts per broadcast domain. Subnetting can also be used as a way to implement security policies quickly and efficiently.

• Classful vs. classless (e.g. CIDR, Supernetting) – A classful network is no longer used today however some of its ideals, such as default subnet mask, are terms still used today. It was used in the early 1980s up until around 1993 when classless inter-domain routing was created, therefore replacing classful networking addressing. With classful addressing, address space was divided into 5 different classes. Each class was coded in the first four bits of the address.

Classless addressing was introduced in 1993 in order to replace classful addressing. The purpose of CIDR was to slow the exhaustion of IPv4 address as well as to reduce the amount of routing tables on routers on the Internet. With CIDR, addresses are classified into three categories.

• NAT – Network Address Translation (NAT) is the process needed in order to modify IP address information located in IP packet headers while the packets are still in transit through a routing device. At its simplest form, NAT is able to provide a one to one translation of IP addresses. In this form IP addresses, IP header checksum and any higher level checksums that include the IP have to be changed while the rest of the packet does not need modification.

• PAT – Port Address Translation (PAT) is needed in order to avoid the ambiguity that may be created when dealing with the returned packets of a one-to-many NAT. With PAT, high level information must be altered in outgoing communications. During this altering, the translation table must be maintained so that the packets can be translated back correctly.

• SNAT – Secure Network Address Translation (SNAT) is the simplest form of NAT and is usually used in combination with PAT. SNAT is widely used because the outside address used is configured which makes determining the address and troubleshooting it much easier. Using SNAT, a one to one translation of an inside local address to an inside global address can be done.

• Public vs. private – IP address assignment now lay within the hands of several different organizations, depending on one’s location in the world. Addresses assigned by the ARIN, APNIC, and RIPE NCC are all public (registered) IP addresses. In order to use the Internet, one of these organizations has to have assigned your computer an IP address. However this is usually done through the work of ISPs.  In the case of private IP addresses, the set addresses are non-routable and are addresses that have been set aside for private use.

• DHCP (static, dynamic APIPA) – Dynamic Host Configuration Protocol (DHCP) is an automatic configuration protocol. Before a computer connected to a network can communication with other network devices, such as other computers, they must be configured properly in order for this communication to be successful. With DHCP a computer is automatically configured which means that a network administrator is not needed in order to properly configure each new computer that is introduced to the network. DHCP also allows for a database that can be consulted to see which computers are connected to the network, a database that can be used to ensure that no two computers are assigned the same IP address.

Computers that are connected to IP networks must be configured before they can communicate with other computers on the network. DHCP allows a computer to be configured automatically, eliminating the need for intervention by a network administrator. It also provides a central database for keeping track of computers that have been connected to the network. This prevents two computers from accidentally being configured with the same IP address.

Addressing schemes

•   Unicast – Unicast addressing is used as the opposite term of broadcast. With a unicast addressing scheme, messaging is only sent to a private or unique resource when requested. Unicast is used by certain media and streaming servers along with some internet radio channels. Of course, unicast could lead to excessive bandwidth use and costs.

• Multicast – Multicast is the most commonly used addressing scheme today. With multicast, information is delivered to a group of destination computers all at once in one transmission. The source is able to create automatic copies which are sent to other network devices, like routers, when needed.

• Broadcast – A broadcast simply refers to how a message is transferred to all devices on a network. Broadcasting can occur in all levels of operation, including both high and low networking.