CompTIA A+ Core Certification: A Simple Guide To Networking - Install and Configure a Basic Wired/Wireless SOHO Network

220-1101: Objective 2.5: Given a scenario, install and configure basic wired/wireless small office/home office (SOHO) networks.
Wireless Ethernet, also known as IEEE 802.11, is the collective name for a group of wireless technologies that are compatible with wired Ethernet; these technologies are referred to as wireless LAN (WLAN) standards. Wireless Ethernet is also known as Wi-Fi, after the Wireless Fidelity (Wi-Fi) Alliance (www.wi-fi.org), a trade group that promotes interoperability among different brands of wireless Ethernet hardware.
The following sections describe factors to consider when implementing these wireless technologies into a SOHO environment.

IP Addressing
The Internet Protocol (IP) is the communication protocol that computers and other devices use to communicate with computers that reside outside their local networks. IPv4 and IPv6 are two current versions of IP addressing that are commonly in use today. All devices that communicate on a local network have a physical address that is unique and unchanging. IP addresses are changeable, logical addresses and are assigned to devices for communicating outside their local networks.

IPv4
An IP version 4 (IPv4) address consists of a group of four numbers that each range from 0 to 255 (for example, 192.168.5.1). An IP address is divided into two sections: the network portion, which is the number of the network the computer is on, and the host portion, which is the individual number of the computer. Using the previous IP address as an example, the 192.168.5 portion typically is the network number, and .1 is the host number. A subnet mask distinguishes between the network portion of the IP address and the host portion. For example, a typical subnet mask for the IP address just used is 255.255.255.0. The 255s correspond to the network portion of the IP address; the 0 corresponds to the host portion, as shown in the table below.

Table:  IPv4 Address and Corresponding Subnet Mask

The subnet mask is also used to define subnetworks, if subnets are being implemented. (Subnetting is beyond the scope of the CompTIA A+ exam.)
Both computers and other networked devices, such as routers and network printers, can have IP addresses. In some cases, a device can have more than one IP address. For example, a router typically has two IP addresses: one to connect the router to a LAN and the other that connects it to the Internet, enabling it to route traffic from the LAN to the Internet and back.
Each number in an IP address is called an octet. An octet is an 8-bit byte. This means that, in the binary numbering system, the number can range from 00000000 to 11111111. For example, 255 is actually 11111111 when converted to the binary numbering system. As another example, 192 decimal equals 11000000 binary. Because an IPv4 address has four octets, it is a 32-bit address. IPv4 supports up to 4.3 billion addresses (that is, 4.3×109).

To convert numbers from decimal to binary and vice versa, use the Windows calculator. Press Windows+R to bring up the Run prompt, and then type calc to open the Windows Calculator application. Several types of calculators are available from the Calculator menu in the upper left. Select the Programmer calculator. Now you can see a list on the left that allows you to change between numbering systems. Simply type any number, and then select the numbering system that you want to convert it to.

Public and Private IP Addresses
Public IP addresses can be discovered and seen by anyone on the Web. Private IP addresses are not routable to the Web and can be used only inside a local area network (LAN). For most SOHO networks, an ISP provides a single public IP address to a customer. The address provided gives access to the Web and is discoverable by anyone on the Internet. That IP address is usually assigned to the interface of the SOHO router that connects to the ISP.
Inside a SOHO network, private IP addresses are used to identify each device on the network. Private addresses are used for a couple reasons. First, the limited number of available public IPv4 addresses is not nearly sufficient to meet demand. IPv4 was not designed with the explosive growth of connected devices in mind, and private addressing was a solution to the address shortage. Second, using private addresses inside a network adds security because devices cannot be discovered from the Internet.

A few easy clues can help determine whether an IP address is public or private, and those come in the first numbers of the IP address.

Private addresses fall in one of three addressing ranges:
10.0.0.0–10.255.255.255
172.16.0.0–172.31.255.255
192.168.0.0–192.168.255.255

Other types of reserved addresses exist, but for a technician working with devices on a private network, knowing the available private addresses is important.
 

Network address translation (NAT) is the process of modifying IP addresses as information crosses a router. Generally, this functionality is built into a router. It hides an entire IP address space (for example, 192.168.0.1 through 192.168.0.255) on the LAN. Whenever an IP address on the LAN wants to communicate with the Internet, the IP address is converted to the public IP address of the router (for example, 68.54.127.95). This way, it appears as if the router is the only device making the connection to remote computers on the Internet, which provides safety for the computers on the LAN. It also allows a single IP address to do the work for many other IP addresses in the LAN.
SOHO routers perform NAT automatically when connected to an IPv4 network. NAT is not necessary on an IPv6 network because IPv6 is much more secure and has no shortage of IP addresses.
Public and private addresses are used in IPv6 as well, but they take a different form.

IPv6
IP version 6 (IPv6) greatly increases the number of available IP addresses for computers, smartphones, and other mobile devices. IPv6 uses 128-bit source and destination IP addresses (compared to 32-bit for IPv4), theoretically enabling up to 340 undecillion addresses (3.4×1038). (This number is largely unimaginable to humans; 340 undecillion is said to exceed the number of grains of sand on Earth.) IPv6 also features built-in security and provides better support for quality of service (QoS) routing, which is important to achieve high-quality streaming audio and video traffic. Windows, macOS, and Linux all support IPv6.

IPv6 Addressing
IPv6 addresses start out as 128-bit addresses that are each then divided into eight 16-bit blocks. The blocks are converted into hexadecimal, and each block is separated from the following block by a colon. Leading zeros are typically suppressed, but each block must contain at least one digit.

Consider a typical IPv6 address:
21DA:D3:0:2F3B:2AA:FF:FE28:9C5A

A contiguous sequence of 16-bit blocks set to zero can be represented by the double colon (::). This technique is also known as zero compression. To determine the number of zero bits represented by the double colon, count the number of blocks in the compressed address, subtract the result from 8, and multiply the result by 16.

An address can include only one zero-compressed block.
This IPv6 address uses the double colon:
FF02::2.
Two blocks exist here: FF02 and 2. So how many zero bits does the double colon represent? Subtract 2 from 8 (8 − 2 = 6) and then multiply 6 by 16 (6 × 16 = 96). This address includes a block of 96 zero bits.

The loopback address on an IPv6 system is 0:0:0:0:0:0:0:1, which is abbreviated as ::1. Thus, if you want to test your network interface in Windows where IPv6 is enabled by default, you can type ping ::1 at a command prompt.

IPv6 Address Types
IPv6 supports three types of addresses: unicast, multicast, and anycast. Five types of unicast addresses exist:
 

Global unicast addresses: Global unicast addresses are used in the same way as IPv4 public addresses. The first 3 bits are set to 001 and the following 45 bits are used for the global routing prefix; these 48 bits are collectively known as the public topology. The subnet ID uses the next 16 bits and the interface ID uses the remaining 64 bits.
Link local addresses: Link local addresses correspond to the Automatic Private IP Addressing (APIPA) address scheme used by IPv4 (addresses that start with 169.254). The first 10 bits are set to FE80 hex, followed by 54 zero bits and 64 bits for the interface ID. Using zero compression, the prefix is thus FE80::/64. As with APIPA, link local addresses are not forwarded beyond the link.
Site local addresses: Site local addresses use the prefix FEC0:: and correspond to IPv4 private address spaces (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16).
Special addresses: Special addresses include unspecified addresses (0:0:0:0:0:0:0:0 or ::), which are equivalent to IPv4’s 0.0.0.0 and indicate the absence of an IP address; a loopback address (0:0:0:0:0:0:0:1 or ::1) is equivalent to the IPv4 loopback address 127.0.0.1.
Compatibility addresses: Compatibility addresses are used when both IPv4 and IPv6 are in use. In the following examples, w.x.y.z is replaced by the actual IPv4 address. An IPv4-compatible address (0:0:0:0:0:0:w.x.y.z or ::w.x.y.z) is used by nodes that support IPv4 and IPv6 communicating over IPv6. An IPv4-mapped address (0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z) represents an IPv4-only node to an IPv6 node. A 6to4 address is used when two nodes running both IPv4 and IPv6 connect over an IPv4 link. The address combines the prefix 2002::/16 with the IPv4 public address of the node. ISATAP can also be used for the connection; it uses the locally administered ID::0:5EFE:w.x.y.z (where w.x.y.z is any unicast IPv4 address, either public or private). Teredo addresses are used for tunneling IPv6 over UDP through network address translation (NAT); they use the prefix 3FFE:831F::/32.
Both IPv4 and IPv6 support multicasting, which enables one-to-many distribution of content such as Internet TV or other types of streaming media. IPv6 multicast addresses begin with FF.
Anycast addressing sends information to a group of potential receivers that are identified by the same destination address. This is also known as one-to-one-to-many association. Anycast addressing can be used for distributed services, such as DNS or other situations in which automatic failover is desirable. IPv6 uses anycast addresses as destination addresses that are assigned only to routers. Anycast addresses are assigned from the unicast address space.

Viewing IP Address Information
To see the IPv4 and IPv6 addresses assigned to a Windows device using both IPv4 and IPv6, use the command-line ipconfig utility at the command prompt. Consider an example of the output from a system using a wireless Ethernet adapter:
 

Wireless LAN adapter Wireless Network Connection:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::5cf1:2f98:7351:b3a3%12
IPv4 Address. . . . . . . . . . . : 192.168.1.155
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1

For more information, see https://technet.microsoft.com/en-us/library/dd392266(WS.10).aspx.

macOS provides IPv4 and IPv6 address information through the TCP/IP tab of the Network utility.



The macOS TCP/IP Tab

Many Linux distros include a GUI-based network utility similar to the one used in macOS, but with any Linux distro (as well as with macOS), you can open Terminal and use the command ifconfig -a to view this information.

Figure shows a portion of the output for a wireless connection.



Linux ifconfig Output for a Wireless Connection

With macOS, use the TCP/IP tab to configure IPv4 or IPv6 address information. macOS uses the term router to refer to the default gateway. Use the DNS tab to configure DNS server information.

With Linux, you can use the network configuration tool provided in the GUI. Alternatively, you can edit the network configuration scripts from Terminal, using the distro’s text editor, if no GUI-based network configuration program is available. Two scripts need to be edited:
ifcfg-connection name identifies IP addresses for IPv4 and IPv6 and the default gateway, as well as other IP settings. It is located in the /etc/sysconfig/network-scripts/ folder. The loopback script is called ifcfg-lo. A separate ifcfg file exists for each connection (wired, wireless, and so on).

The file resolv.conf identifies DNS servers. It is located in the /etc/ folder.
For the syntax, see the documentation for the distribution in use.

A small office/home office (SOHO) wired or wireless router can provide a secure way for users to access the Internet and local network resources; it can also become a magnet for attack. The difference is in how the router is configured. The following sections look at how to configure SOHO routers to meet typical network requirements.

To configure a router’s settings, connect to the router either with an Ethernet cable or wirelessly, using the manufacturer’s instructions on the default IP address to use. To connect to the router’s web interface, open a browser, enter the IP address of the router in the address bar, and press Enter.

APIPA IP Addresses/Link Local Addresses
Most IP networks use addresses provided automatically by the Dynamic Host Configuration Protocol (DHCP). However, if the DHCP server becomes unavailable and an alternate IP address has not been set up, devices on the network assign themselves Automatic Private IP Addressing (APIPA) or link local addresses. These addresses are in the IPv4 address range 169.254.0.1 to 169.254.255.254 (with the subnet mask 255.255.0.0); the IPv6 version is called a link local address and has the FE80::/64 prefix. A device with an APIPA address cannot connect to the Internet.
If a DHCP problem causes APIPA/link local addresses to be assigned, you can resolve the problem by checking the device’s network connection and using the ipconfig /release and ipconfig /renew commands at the command prompt. This causes the computer to obtain a new IP address from the DHCP server. If these actions do not solve the problem, the DHCP server (often located in the router on a SOHO network) should be checked and restarted, if necessary.
APIPA was originally developed by Microsoft, but it is now a standard (RFC 3927) that macOS and Linux also support.

Dynamic vs. Static IP Addresses
The term static means “unchanging” or “always the same.” Dynamic means “constantly changing.” These terms describe the two most common ways to configure a computer’s IP address settings:
Static IP address: Assigned to a device by the administrator and not subject to change until reconfigured by the administrator. Note that more than just the IP address must be configured; other areas are the subnet mask, the default gateway, and DNS servers.
Dynamic (DHCP server-assigned) IP address: Assigned by a DHCP server and likely to change each time a device leaves and then rejoins the network, or when the address is used beyond its lease time and expires.
 

Table: Static vs. Dynamic IP Addressing

Windows, macOS, and Linux default to using dynamic IP addresses. As Table above makes clear, this is the preferred method for configuring a TCP/IP network. Use a manually assigned IP address if a DHCP server (which provides IP addresses automatically) is not available on the network or if you need to configure a firewall or router to provide different levels of access to some systems (in this case, you must specify those systems’ IP addresses).
For the 220-1101 exam, be sure you understand the difference between static and dynamic IP addressing and know where to go within a given operating system to set or change client-side DHCP, DNS, subnet mask, and default gateway settings.
Routers, wireless gateways, and computers that host a shared Internet connection with Windows Internet Connection Sharing or a third-party sharing program all provide DHCP services to other computers on the network.

To configure an IP address in Windows, access the Internet Protocol Properties window. This window contains several dialogs used to make changes to an IP address. To open the General tab of the Internet Protocol Properties window, open Network Connections, right-click the network connection, select Properties, click Internet Protocol v4 (TCP/IPv4) or TCP/IPv6 in the list of protocols and features, and click Properties.
IP configuration in Linux is performed by editing the /etc/network/interfaces file. If you use a GUI that features a Network configuration panel, you can use it to make changes for you.

To configure TCP/IP in macOS, go to System Preferences, open the Network panel, and select the appropriate tab.

DHCP
By default, SOHO routers have the DHCP service turned on so they can provide IP addresses to any wired or wireless devices that connect. Most routers enable you to specify the range and number of IP addresses available via DHCP.

Figure below illustrates a router with DHCP enabled and a range of IP addresses that the DHCP server can assign. In this example, the default address of the router is 192.168.1.1 and the subnet mask is 255.255.255.0. This means that the router has the first address on the 192.168.0 network, which is a private network that cannot be used on the Internet. As shown in the router settings, when devices join the network, DHCP assigns addresses in the range 192.168.1.100 to 192.168.1.149.



Configuring DHCP to Provide a Range of 50 IP Addresses

If a router does not have sufficient IP addresses for the devices that need to connect to it, devices that arrive after the pool of addresses is used up do not receive IP addresses; instead, the router switches to Automatic Private IP Addressing (APIPA), using the nonroutable IP address range 169.254.x.x.
When you need to use static IP addresses on some devices, be sure to reserve some IP addresses and keep them out of the range of addresses assigned by the DHCP server. For example, in the network illustrated in Figure 2-9, IP addresses below 100 and above 149 in the 192.168.1.x network could be used for devices that need static IP addresses.

IP Addressing
A SOHO router comes with a default IP address. This IP address is a special type known as a private address.

NIC Configuration
A PC can have several different NICs, to make it possible to connect to networks over the wire, via Wi-Fi, or virtually. After you select the NIC that matches the method of connecting, you can choose the protocol and configure network access.

NIC Configuration Steps
The steps for configuring a NIC follow:
Step 1. Click the Windows icon and select the Windows Settings gear.
Step 2. In the Windows Settings window, select the Network & Internet Link.
Step 3. When you see the different connection options, select the one you want and click Change Adapter Options, on the right side of the window.
Step 4. Choose the adapter you want to configure (in this case, Ethernet) and click the Properties button. A list of items available to the NIC appears. In the example, note that both IPv4 and IPv6 are checked, making them available to the NIC.
Step 5. Double-click Internet Protocol Version 4 (TCP/IPv4). You now see the window where the IP address is configured either dynamically or statically (see Figure).



Configuring a Static IP Address

Step 6. By default, the Obtain an IP Address Automatically option is selected. This option dynamically assigns an IP address from a DHCP server. To configure the device with a static IP address, select Use the Following IP Address and enter the IP address, subnet mask, and default gateway; click OK to accept any changes.

End-User Device Configuration
The steps for configuring a NIC are essentially the same steps used for other end-user devices, such as printers and mobile phones. If the default on an end-user device is DHCP, the device is likely to autoconfigure. If the device needs to be configured, the process is mostly the same as described for NICs. To access the configuration windows, you might need to visit the manufacturer’s support site.

Cable/DSL Modem
Setting up a cable modem or DSL modem is a fairly simple task on the user’s end. Most SOHO networks use a wireless router, and it must be connected to the modem. Simply plug one end of an Ethernet cable into the cable or DSL modem and then plug the other end into the RJ-45 jack labeled as Internet. Attach the local devices to the wireless router with Ethernet cables in the remaining ports or via Wi-Fi.