A+ Exam Objective 2.5 Given a scenario, install and configure basic wired/wireless small office/home office (SOHO) networks.
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Here we will dive into the concepts covered in A+ 220-1101 sub-objective 2.5 “Given a scenario, install and configure basic wired/wireless small office/home office (SOHO) networks”. We will look at the properties that make TCP/IP the robust protocol set that it is and how TCP/IP is used to manage networks from the smallest of LANs all the way up to the World Wide Web.
IP Addressing
The TCP/IP protocol stack is the foundation of the World Wide Web and most local networks. Each host or client connecting to a network such as the Web needs a unique address. Duplication of addresses causes a failure of one or both hosts.
The IP protocol is used for host identification. There are two types of IP addresses being actively used: IPv4 and IPv6. The original addressing organization was IPv4 which, while still heavily used today, has exceeded its capacity to serve the rapidly growing number of internet-connected computers and devices. In 1999, the IANA (Internet Assigned Numbers Authority) began the deployment of the IPv6 protocol.
Internet Protocol version 4 – IPv4
An IP address consists of 32 bits, separated using a dotted decimal notation into four octets with dots (periods). The numbers are assigned in binary, where you could see a number like 11011111.10111010.11011011.00000011. For each octet, the maximum value is 255 (all 1’s in binary). The binary number is then converted into decimal numbers that are easier for humans to recognize. The example above would translate to a decimal value of 13.168.155.3.
Each octet can assign eight binary values of zero or one. A good way to verify that your TCP/IP protocol stack has been correctly installed with a new network card is by pinging its loopback address. The IPv4 address is 127.0.0.1 and by pinging this, you can check the installation and functionality of the interface.
Internet Protocol version 6 – IPv6
In order to address the inevitable exhaustion of IPv4 addresses, the deployment of IPv6 began in 1999, providing 340 undecillion or 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses. The IPv6 address is 128-bits in length and although it is actually a binary address, the use of a 128-bit binary address is impractical for human interpretation. Instead, IPv6 is expressed in hexadecimal numbers separated by colons and consists of eight groups of hexadecimal values. Hexadecimal numbering allows for up to 16 case-sensitive values (0-9 and A-F) to be expressed for each digit as opposed to the standard base 10 decimal system. Each hexadecimal digit represents four digits or bits of binary. Each of the eight groups of an IPv6 address represents 16 bits (Two four-bit values). A typical IPv6 address will look something like this, 2002:1F93:AF34:DA4C:0000:0000:0000:CADE. For IPv6, the loopback function is the same as IPv4 using an IPv6 address. This address is represented as 0::1 or even simply ::1.
In IPv6 shorthand notation, groups of zeroes are represented by double colons. Our example can be written as 2002:1F93:AF34:DA4C:: CADE. Note that the double colons substituted for three groups of zeroes. Only one set of colons is allowed in an IPv6 address. Here, the binary value of the first block would be 0010 0000 0000 0010. The Interface Identifier or node address is represented by the last 64-bits of the 128-bit address. In our example, the node is identified as 222 or binary 11011110.
Public and Private Addresses
The IANA has reserved the following address ranges for private networks. The address ranges are listed below. The best example of private network deployment is with SOHO or at home where you are provided a single, public IP address from an internet service provider (ISP) and use NAT/PAT to assign private numbers to use the public address for computers and phones.
Private Addresses
The IANA has reserved the following address ranges for private networks. This means any address within these ranges is private and non-routable.
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255
Unique Local Addresses – ULA
The address block of fc00::/7 is reserved by IANA for private use as Unique Local Addresses (ULA). This means that the first block assigned will be fd00::/8.
APIPA/link local
Best described as Zero configuration networks, APIPA and link-local addresses are assigned to hosts when there is no reachable DHCP server and there is no manual address assignment. IPv4 uses the address range 169.254.1.0 to 169.254.254.255 and IPv6 uses the block fe80::/64, in other words, the address fe80 and enough zeroes to make 64 bits. You may see a % sign followed by a number in the IPv6 link-local address. This is a Zone ID network identifier. This is useful as many computers have wired and wireless connections. Each NIC or device on a network segment is given an ID to determine which interface to send particular traffic out on. APIPA and link-local addresses are non-routable.
Client-side DHCP vs Static Addressing
The most common IPv4 or IPv6 TCP/IP addressing method is DHCP (Dynamic Host Configuration Protocol). On a work network, there is usually an assigned DHCP server. Residential or SOHO implementations use the router provided by the ISP to perform this function. DHCP assigns or leases a unique IP address to each host. The duration of the lease is determined by the network administrator, otherwise is weekly by default. DHCP will define the internet gateway and Domain Name Server to be used. This means that your machine may not get the same IP address when rebooted or otherwise disconnected, however, the DNS and Gateway settings will remain.
The DHCP server has an available pool of addresses available to assign to clients (hosts) that attempt to connect to the network. The client broadcasts a UDP discovery packet for an address to all connected networks. All DHCP servers will offer an address to the client. The client will accept the offer from the nearest server by requesting a lease and that server will lease that address to the client.
The address assignment process is identical for both IPv4 and IPv6 addressing and only the address format will be different. This greatly simplifies network management and the other option is Static IP addressing. Should you need a client to maintain a specific IP address, you can create a DHCP reservation in order to hold that address permanently.
Static IP addressing is preferable for Web servers and Internet gateways where you would like to be able to consistently locate the machine. Any device that is accessed consistently by users should be statically addressed. Otherwise and depending on the size of the network, this would be an incredibly labor-intensive task that would require documentation to avoid duplication of addresses. If it isn’t memorized, look up the Gateway and DNS servers on a neighboring machine.
Gateways and DNS
If known, network clients can access computers on the local network or internet using its IP address. Internet access is dependent on the configuration of the Gateway on the network, a device that handles off-network requests and forwards them to the internet. The address of this device is part of the client configuration as is the DNS server address.
It is improbable that the average person knows the IP address of the sites they wish to visit or even devices or machines on the network. Name resolution solves this problem by using a DNS (Domain Name Server) to resolve the IP addresses into names. A DNS server maintains a list of machines along with their IP addresses and their domain names. For example, a DNS server would have an entry that read www.mysite.com = 202.22.222.2. With that information, any user can type in the address using the domain name and the server will look it up and translate the address. If the name is not known to the server, it will request it from the other DNS servers known to it. Once a device successfully connects, this information is cached locally. Don’t forget that a Default Gateway and a DNS Server must be configured in order for your settings to work properly.
Gateway
If known, network clients can access computers on the local network or internet using its IP address. Internet access is dependent on the configuration of the Gateway on the network, a device that handles off-network requests and forwards them to the internet. The address of this device is part of the client configuration as is the DNS server address.
And that wraps up our ExamNotes for A+ Sub-objective 2.5. Good luck on the exam!
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