CompTIA Network+ N10-006 Chapter 5
universal naming convention (UNC)
A WINS server could then be used to resolve the network device name of server1 to a corresponding IP address. The path of \\server1\hrdocs is in universal naming convention (UNC) form where you are specifying a network device name (for example, server1) and a resource available on that device (for example, hrdocs). More and more companies today are transitioning to DNS even for internal network name resolution.
Classful masks
A classful masks is the default subnet mask applied to Class A, B, and C IPv4 networks. Speciffically, Class A networks have a classful masks of 255.0.0.0. Class B networks have a classful masks of 255.255.0.0 and Classful C networks have a classful masks of 255.255.255.0
Octet
A grouping of 8 bits. An IPv4 address consists of four octets (that is, a total of 32 bits).
Bookstrap Protocol (BOO TP)
A legacy broadcast-based protocol used by networked devices to obtain IP address information
Link-local IP address
A link-local IP address is a nonroutable IP address usable only on a local subnet.
Prefix notation
A method of indicating of how many bits are in a subnet mask. For example, /24 is prefix notation for a 24-bit subnet mask. Prefix notation is also known as slash notation.
Dotted-decimal notation
A method of writing in IPv4 address or subnet mask, where groups of 8 bits (called octets) are separated by periods.
Multicast
A multicast communication flow is a one-to-many flow.
Reverse Address Resolution Protocol (RARP)
A prot ocol rendered obsolete by BOOTP and DHCP . Resolution Protocol (ARP) requests a MAC address that corresponds to a known IP address, RARP requested an IP address (from a preconfigured host) that corresponded to a station's MAC address. Although RARP did allow a station to dynamically obtain an IP address, both BOOTP and DHCP offer additional features.
static configuration
A simple way of configuring a PC, for example, with IP address parameters is to statically configure that information.
Zeroconf
A technology that performs three basic functions: assigning link-local IP address, resolving computer names to IP addresses, and locating network services.
unicast
A unicast communication flow is a one-to-one flow.
Automatic Private IP Addressing (APIPA)
Allows a networked device to self-assign an IP address from the 169.254.0.0 network. Note that the address is only usable from the device's local subnet (meaning that the IP address is not routable)
IPv4 Address Structure
An IPv4 address is a 32-bit address. However, rather than writing out each individual bit value, the address is typically written in dotted-decimal notation.
IPv6 Address Structure
An IPv6 address has the following address format, where X = a hexadecimal digit in the range of 0 to F: XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX 4 bits per digit * 4 digits per field * 8 fields = 128 bits in an IPv6 address IPv6 addresses can be difficult to work with because of their size. Fortunately, the following rules exist for abbreviating these addresses: Leading 0s in a field can be omitted. Contiguous fields containing all 0s can be represented with a double colon. (Note that this can be done only once for a single IPv6 address.) For example, consider the following IPv6 address: ABCD:0123:4040:0000:0000:0000:000A:000B Using the rules for abbreviation, the IPv6 address can be rewritten as follows: ABCD:123:4040::A:B Also, the Extended Unique Identifier (EUI-64) format can be used to cause a router to automatically populate the low-order 64 bits of an IPv6 address based on an interface's MAC address. IPv6 Address Types IPv6 globally routable unicast addresses start with the first 4 hex characters in the range of 2000 to 3999. An IPv6 link-local address is also used on each IPv6 interface. The link-local address begins with FE80. The multicast addresses begin with FF as the first two hex characters. IPv6 can use autoconfiguration to discover the current network and select a host ID that is unique on that network. IPv6 can also use a special version of DHCP for IPv6. The protocol that is used to discover the network address and learn the Layer 2 address of neighbors on the same network is Neighbor Discovery Protocol (NDP). IPv6 Data Flows IPv6 has three types of data flows: Unicast Multicast Anycast The following sections summarize the characteristics of each address type. Unicast With unicast, a single IPv6 address is applied to a single interface, as illustrated in Figure 5-21. The communication flow can be thought of as a one-to-one communication flow. Figure 5-21 IPv6 Unicast Example In Figure 5-21, a server (AAAA::1) is sending traffic to a single client (AAAA::2). Multicast With multicast, a single IPv6 address (a multicast group) can represent multiple devices on a network, as shown in Figure 5-22. The communication flow is a one-to-many communication flow. Figure 5-22 IPv6 Multicast Example In Figure 5-22, a server (AAAA::1) is sending traffic to a multicast group (FF00::A). Two clients (AAAA::2 and AAAA::3) have joined this group. Those clients receive the traffic from the server, while any client that did not join the group (for example, AAAA::4) does not receive the traffic.
Anycast
An anycast communication flow is one-to-nearest (from the perspective of a router's routing table
Bootstrap Protocol (BOOTP for short)
An early option for performing this automatic assignment of IP addresses
BOOTP
BOOTP was developed as a method of assigning IP address, subnet mask, and default gateway information to diskless workstations. In the early days of Microsoft Windows (for example, Microsoft Windows 3.1), Microsoft Windows did not natively support TCP/IP. To add TCP/IP support, an add-on TCP/IP application (for example, Trumpet Winsock) could be run. Such an application would typically support BOOTP. When a device needed to obtain IP address information, a BOOTP broadcast would be sent out from the device needing an IP address. If a BOOTP server (BOOTPs) received the broadcast, it could match the source MAC address in the received frame (the MAC address from the device wanting to obtain an IP address) with a corresponding IP address, in a database stored on the BOOTP server. The BOOTPs would then respond to the requesting client with IP address information. Because BOOTP requests were based on broadcasts, by default, a BOOTP request could not propagate beyond a device's local subnet. However, most enterprise-class routers can be configured to forward selected broadcast types, including BOOTP broadcasts.
IPv6
Beyond the increased address space, IPv6 offers many other features: Simplified header IPv4 header uses 12 fields IPv6 header uses 5 fields No broadcasts No fragmentation (performs MTU discovery for each session) Can coexist with IPv4 during a transition Dual stack (running IPv4 and IPv6 simultaneously) IPv6 over IPv4 (tunneling IPv6 over an IPv4 tunnel) . Using Teredo tunneling, an IPv6 host could provide IPv6 connectivity even when the host is directly connected to an IPv4-only network. Miredo is a client that can be used to implement the Teredo protocol and is included in many versions of Linux. IPv6/IPv4 tunneling is often referred to as 6to4 or 4to6 tunneling, depending on which protocol is being tunneled (IPv4 or IPv6).
Borrowed bits
Bits added to a classful subnet mask
Broadcast
Broadcast traffic travels from a single source to all destinations on a network (that is, a broadcast domain). A broadcast address of 255.255.255.255 might seem that it would reach all hosts on all interconnected network. However, 255.255.255.255 targets all devices on a single network, specifically the network local to the device sending a packet destined for 255.255.255.255.
Dynamic Host Configuration Protocol (DHCP)
Dynamically assigns IP address information (for example, IP address, subnet mask, DNS server's IP address, and default gateway's IP address) to network devices.
Subnet Mask Notation
ExTable 5-22 Dotted-Decimal and Prefix-Notation Representations for IPv4 Subnets Dotted-Decimal Notation Prefix Notation 255.0.0.0 /8 (Classful subnet mask for Class A networks) 255.128.0.0 /9 255.192.0.0 /10 255.224.0.0 /11 255.240.0.0 /12 255.248.0.0 /13 255.252.0.0 /14 255.254.0.0 /15 255.255.0.0 /16 (Classful subnet mask for Class B networks) 255.255.128.0 /17 255.255.192.0 /18 255.255.224.0 /19 255.255.240.0 /20 255.255.248.0 /21 255.255.252.0 /22 255.255.254.0 /23 255.255.255.0 /24 (Classful subnet mask for Class C networks) 255.255.255.128 /25 255.255.255.192 /26 255.255.255.224 /27 255.255.255.240 /28 255.255.255.248 /29 255.255.255.252 /30
Hexadecimal
Hexadecimal numbers are base 16 numbers with values at each place range from 0 and F. In hexadecimal number system, numbers above 9 are expressed with letters A through F. Like the other numbering systems, place values are used with the first place value being 160, followed by 161, 162, and so on. Hexadecimal number are mostly encountered in MAC addresses.
dotted-decimal notation
IP address of 10.1.2.3. This address is written in dotted-decimal notation. Notice that the IP address is divided into four separate numbers, separated by periods. Each number represents one-fourth of the IP address. Specifically, each number represents an 8-bit portion of the 32 bits in the address
Unicast
Most network traffic is unicast in nature, meaning that traffic travels from a single source device to a single destination device. Figure 5-4 illustrates an example of a unicast transmission.
Resolving computer names to IP addresses
Multicast Domain Name Service (mDNS) is an example of a technology that can resolve computer names to their corresponding IP address on a local subnet, without the aid of a DNS server or a WINS server.
Calculating the Number of Available Hosts
Number of assignable IP address in a subnet = 2h - 2, where h is the number of host bits in the subnet mask Number of host bits = 32 - Number of bits in subnet mask Number of assignable IP addresses in a subnet = 2h - 2
Calculating the Number of Created Subnets
Number of created subnets = 2s, where s is the number of borrowed bits Number of borrowed bits = Bits in custom subnet mask - Bits in classful subnet mask Number of borrowed bits = 28 - 24 = 4
Octal
Octal numbers are base 8 numbers and use the numbers 0 to 7. These are more often used by programmers and are not typically used when viewing networking addresses or routes.
Converting a Binary Number to a Decimal Number
Only the 128, 16, 4, and 2 columns contain a 1, and all the other columns contain a 0. If you add all the column headings containing a 1 in their column (that is, 128 + 16 + 4 + 2), you get a result of 150. Therefore, you can conclude that the binary number of 10010110 equates to a decimal value of 150.
IP number Registery
Publicly routable IP addresses are globally managed by the Internet Corporation for Assigned Names and Numbers (ICANN) nonprofit corporation. ICANN does not directly assign a block of IP addresses to your Internet service provider (ISP), but assigns a block of IP addresses to a regional Internet registry. One example of a regional Internet registry is the American Registry for Internet Numbers (ARIN), which acts as an Internet registry for North America. The Internet Assigned Numbers Authority (IANA) is yet another entity responsible for IP address assignment. IANA is operated by ICANN and is responsible for IP address assignment outside of North America.
Classless interdomain routing (CIDR)
Shortens a classful subnet mask by removing right-justified 1s from a classful mask. As a result, CIDR allows contiguous classful networks to be aggregated. This process is sometimes called route aggregration.
Private IP addresses
Specific Class A, B, and C networks have been designed for private use. Although these networks are routable (with the exception of the 169.254.0.0 - 169.254.255.255 address range), within the organization, service providers do not route these private networks over the public Internet.
classless interdomain routing (CIDR)
Specifically, CIDR shortens a classful subnet mask by removing 1s from the classful mask. As a result, CIDR allows contiguous classful networks to be aggregated. This process is sometimes called route aggregation.
Dynamic Configuration
Statically assigning IP address information to individual networked devices can be time consuming, error-prone, and lacks scalability. Instead of static IP address assignments, many corporate networks dynamically assign IP address parameters to their devices
Converting a Decimal Number to a Binary Number
Step 1. Ask the question, "Is 167 equal to or greater than 128?" Because the answer is yes, you place a 1 in the 128 column, as shown in Table 5-3 and subtract 128 from 167, which yields a result of 39. Table 5-3 Binary Conversion Example 2: Step 1 Step 2. Now that you are done with the 128 column, move (to the right) to the 64 column. Ask the question, "Is 39 equal to or greater than 64?" Because the answer is no, you place a 0 in the 64 column, as shown in Table 5-4, and continue to the next column (the 32 column). Table 5-4 Binary Conversion Example 2: Step 2 Step 3. Under the 32 column, ask the question, "Is 39 equal to or greater than 32?" Because the answer is yes, you place a 1 in the 32 column, as shown in Table 5-5, and subtract 32 from 39, which yields a result of 7. Table 5-5 Binary Conversion Example 2: Step 3 Step 4. Now you are under the 16 column and ask, "Is 7 equal to or greater than 16?" Because the answer is no, you place a 0 in the 16 column, as shown in Table 5-6, and move to the 8 column. Table 5-6 Binary Conversion Example 2: Step 4 Step 5. Similar to the 16 column, the number 7 is not equal to or greater than an 8. So, a 0 is placed in the 8 column, as shown in Table 5-7. Table 5-7 Binary Conversion Example 2: Step 5 Step 6. Because 7 is greater than or equal to 4, a 1 is placed in the 4 column, as shown in Table 5-8, and 4 is subtracted from 7, yielding 3 as the result. Table 5-8 Binary Conversion Example 2: Step 6 Step 7. Now under the 2 column, you ask the question, "Is 3 greater than or equal to 2?" Because the answer is yes, you place a 1 in the 2 column, as shown in Table 5-9, and subtract 2 from 3. Table 5-9 Binary Conversion Example 2: Step 7 Step 8. Finally, in the rightmost column (that is, the 1 column), you ask whether the number 1 is greater than or equal to 1. Because it is, you place a 1 in the 1 column, as shown in Table 5-10. Table 5-10 Binary Conversion Example 2: Step 8 You can now conclude that a decimal number of 167 equates to a binary value of 10100111. In fact, you can check your work by adding up the values for the column headings that contain a 1 in their column. In this example, the 128, 32, 4, 2, and 1 columns contain a 1. If you add these values, the result is 167 (that is, 128 + 32 + 4 + 2 + 1 = 167).
steps for calculating subnets
Step 1. Determine the interesting octet by determining the last octet in the subnet mask to contain a 1. Step 2. Determine the block size by subtracting the decimal value in the subnet's interesting octet from 256. Step 3. Determine the first subnet by setting all the borrowed bits (which are bits in the subnet mask beyond the bits in the classful subnet mask) to 0. Step 4. Determine additional subnets by taking the first subnet and counting by the block size increment in the interesting octet.
Subnet Octet Values
Subnet Octet Value Number of Contiguous Left-Justified Ones 0 0 128 1 192 2 224 3 240 4 248 5 252 6 254 7 255 8 consider the subnet mask of 255.255.192.0. Because each of the first two octets has a value of 255, you know that you have 16 1s from the first two octets. You then recall that a value of 192 in the third octet requires two 1s from that octet. By adding the 16 1s from the first two octets to the two 1s from the third octet, you can determine that the subnet mask of 255.255.192.0 has a corresponding prefix notation of /18
Automatic Private IP Addressing
The APIPA feature allows a networked device to self-assign an IP address from the 169.254.0.0/16 network. Note that this address is usable only on the device's local subnet. (The IP address is not routable.) APIPA was designed as a solution for quickly setting up a localized network without the need to configure a DHCP server or the need to statically assign IP address information.
Subnet mask
The IP address component that determines which bits refer to the network and which bits refer to the host. A subnet mask typically consists of a series of contiguous 1s followed by a set of continuous 0s. In total, a subnet mask contains 32 bits, which correspond to the 32 bits found in an IPv4 address. The 1s in a subnet mask correspond to network bits in an IPv4 address, and 0s in a subnet mask correspond to host bits in an IPv4 address.
Default gateway
The IP address of a router (or multilayer switch) to which a networked device sends traffic destined for a subnet other than the device's local subnet.
Block Size
The number of IP addresses in a subnet, including the subnet's address and the subnet's directed broadcast address.
Binary Conversion
There are eight columns, representing the 8 bits in an octet. The column headings are the powers of 2 (the powers of 0-7), beginning with the rightmost column. Specifically, 2 raised to the power of 0 (20) is 1. (In fact, any number raised to the 0 power is 1.) If you raise a 2 to the first power (21), that equals 2. A 2 raised to the second power (that is, 2 * 2, or 22) is 4. This continues through 2 raised to the power of 7 (that is, 2 * 2 * 2 * 2 * 2 * 2 * 2, or 27), which equals 128. This table can be used for converting binary numbers to decimal and decimal numbers to binary.
Private Addressing
When an organization is assigned one or more publicly routable IP addresses by its service provider, that organization often needs more IP addresses to accommodate all of its devices. One solution is to use private IP addressing within an organization, in combination with Network Address Translation (NAT). Specific Class A, B, and C networks have been designed for private use. Although these networks are routable (with the exception of the 169.254.0.0-169.254.255.255 address range), within the organization, ISPs do not route these private networks over the public Internet. Table 5-20 shows these IP networks reserved for internal use. NOTE: The 169.254.0.0-169.254.255.255 address range is not routable. Addresses in the range are only usable on their local subnet and are dynamically assigned to network hosts using the Automatic Private IP Addressing (APIPA) feature, which is discussed later in this section.
borrowed bits
When you add bits to a classful mask, the bits you add are referred to as borrowed bits. The number of borrowed bits you use determines how many subnets are created and the number of usable hosts per subnet.
IPv4, IP version 4
a 32 bit IP address, Some of those bits represent the network on which a device resides.The remaining bits represent the device itself or the host itself on that network
binary number
a number composed of ones and zeroes into a decimal number and vice versa
Network Address
all host bits are set to 0s. meaning that the 8 leftmost bits in the subnet mask are 1s. For example, just being told that a device has an IP address of 10.1.2.3 does not tell you the network on which the IP address resides. To know the network address, you need to know the subnet mask, which could be written in dotted-decimal notation or in prefix notation (also known as slash notation). In the example, where we have an IP address of 10.1.2.3 and an 8-bit subnet mask, the IP address could be written as 10.1.2.3 255.0.0.0 or 10.1.2.3 /8. Similarly, the network address could be written as 10.0.0.0 255.0.0.0 or 10.0.0.0 /8.
IP Addressing Components
an IP address has two portions: a network portion and a host portion. A subnet mask is required to delineate between these two portions. In addition, if traffic is destined for a different subnet than the subnet on which the traffic originates, a default gateway needs to be defined. o summarize, network devices (for example, an end-user PC) can benefit from a variety of IP address parameters, such as the following: IP address Subnet mask Default gateway Server addresses
IP Address
composed of two types of addresses: a network address and a host address.
Classes of Addresses
default subnet masks with which you should be familiar. The default subnet mask for a given IP address is solely determined by the value in the IP address's first octet. You might have noticed that in the ranges of values in the first octet, the number 127 seems to have been skipped. The reason is that 127 is used as a loopback IP address, meaning a locally significant IP address representing the device itself. For example, if you were working on a network device and wanted to verify that device had a TCP/IP stack loaded, you could attempt to ping an IP address of 127.1.1.1. If you received ping responses, you could conclude that the device is running a TCP/IP stack. The ping function is discussed in Lesson 10, "Command-Line Tools."
Classful masks
different classes of addresses. Classes A, B, and C are those ranges of addresses assigned to network devices. Class D addresses are used as destination IP addresses (that is, not assigned to devices sourcing traffic) for multicast networks, and Class E addresses are reserved for experimental use. The default subnet masks associated with address classes A, B, and C
Dynamic Host Configuration Protocol (DHCP)
does not require a statically configured database of MAC address to IP address mappings. a DHCP server can educate a DHCP client about the IP address of a WINS server, or even an administrator-defined parameter (for example, the IP address of a TFTP server from which a configuration file could be downloaded). like BOOTP, DHCP's initial request is a broadcast, requiring a client's local router be configured to appropriately forward DHCP requests to a DHCP server if that DHCP server is not on the local subnet of the requesting client. In setting up a DHCP server, you would identify a range of IP addresses to hand out, and this would be referred to as the scope. In addition, a DHCP server can be configured to have reservations, which will assign a specific IP address to a specific Layer 2 Ethernet MAC address. The lease time can also be configured and is usually set to one day. The DHCP server can also provide options such as DNS server addresses, the default gateway to use, domain suffixes to use, and more. If a DHCP client is not on the same subnet as a DHCP server, a router or other device that is connected to the same subnet as the DHCP client can be configured as a DHCP relay and can take the discover packet from the client and route it to where the DHCP server is. This feature is also sometimes referred to as IP helper.
Multicast
provides an efficient mechanism for a single host to send traffic to multiple, yet specific, destinations
Locating network services
samples of service discovery protocols include the standards-based Service Location Protocol (SLP), Microsoft's Simple Service Discovery Protocol (SSDP), and Apple's DNS-based Service Discovery (DNS-SD).
Slash notation
see prefix notation - A method of indicating of how many bits are in a subnet mask. For example, /24 is prefix notation for a 24-bit subnet mask. Prefix notation is also known as slash notation.
directed broadcast address
which targets all devices in a remote network. For example, the address 172.16.255.255 /16 is a directed broadcast targeting all devices in the 172.16.0.0 /16 network
