Chapter 6: Applied Networking

Network Address Translation (NAT)

A protocol used to convert a private IP address to an Internet-routable address

IP Adress

IP addressing is assigned by network administrators based on the location within the network. When a device moves from one network to another, its IP address will most likely change. An IP version 4 (IPv4) address is 32 bits and represented in dotted decimal notation. An IP version 6 (IPv6) address is 128 bits and is represented in hexadecimal format, as shown in Figure 3.

IPv4 APIPA Address

If your Windows computer cannot communicate with a DHCP server to obtain an IPv4 address, then Windows automatically assigns an Automatic Private IP Addressing (APIPA) address. This link-local address is in the range of 169.254.0.0 to 169.254.255.255.

Network components

Includes wired and wireless network interface cards (NIC) and network devices such as switches, wireless access points (APs), routers, multipurpose devices, and more.

ICMP (Internet Control Message Protocol)

Internet Control Message Protocol (ICMP) is used by devices on a network to send control and error messages. There are several different uses for ICMP, such as announcing network errors, announcing network congestion, and troubleshooting.

Network design

Involves knowing how networks are interconnected to support the needs of a business. For instance, the needs of a small business will differ greatly from the needs of a large business.

MAC address filtering

MAC address filtering specifies exactly which device MAC addresses are allowed to or blocked from sending data on your network. Many wireless routers only give you the option of allowing or blocking MAC addresses, but not both. Technicians will typically configure allowed MAC addresses. The MAC address for your Windows computer can be found with the ipconfig /all command, as shown in Figure 1.

IPv6 APIPA Address

The IPv6 link-local address enables your device to communicate with other IPv6-enabled devices on the same network and only on that network. Unlike IPv4, every IPv6 enabled device is required to have a link-local address. IPv6 link-local addresses are in the range of fe80:: to febf::. For example, in the figure, the links to other networks are down (not connected) as notate by the red Xs. However, all the devices on the LAN can still use link-local IPv6 addresses to communicate with each other.

MAC address

The MAC address is hard-coded onto the Ethernet or wireless network interface card (NIC) by the manufacturer. The address stays with the device regardless of what network the device is connected to. A MAC address is 48 bits and can be represented in one of the three hexadecimal formats shown in Figure 2.

Universal Plug and Play (UPnP)

Universal Plug and Play (UPnP) is a protocol that enables devices to dynamically add themselves to a network without the need for user intervention or configuration. Although convenient, UPnP is not secure. The UPnP protocol has no method for authenticating devices. Therefore, it considers every device trustworthy. In addition, the UPnP protocol has numerous security vulnerabilities. For example, malware can use the UPnP protocol to redirect traffic to different IP addresses outside your network, potentially sending sensitive information to a hacker.

DMZ

A demilitarized zone (DMZ) is a network that provides services to an untrusted network. An email, web, or FTP server is often placed into the DMZ so that the traffic using the server does not come inside the local network. This protects the internal network from attacks by this traffic but does not protect the servers in the DMZ in any way. It is common for a firewall to manage traffic to and from the DMZ.

Quality of Service (QoS)

Many home and small office routers have an option for configuring Quality of Service (QoS). By configuring QoS, you can guarantee that certain traffic types, such as voice and video, are prioritized over traffic that is not as time-sensitive, such as email and web browsing. On some wireless routers, traffic can also be prioritized on specific ports.