Networking: Chapter 4.1 - IP Addressing

network address

*.*.*.0 The first valid IP address on the network. This address is used for routing purposes to identify the network.

broadcast address

*.*.*.255 The last valid IP address on a network. It is reserved for broadcast functions. Any packet sent to this address will be sent to all devices on the network.

subnetting benefits

- Increased security - Easier network management - Improved netowrk performance - Separation of departments

supernetting advantages

- Reduces the size of routing tables. - Simplifies the network overview. - Decreases the CPU and RAM resources on the routers. - Improves network performance.

converting binary to hexadecimal

1. Break the binary string into nibbles (4-bit sections). 2. Convert the nibbles. Example: Convert the binary string 11000111. Split the string into two nibbles. - 1100 - 0111 Solve for each nubble using the first four values starting from the right on the binary to decimal conversion chart. - 1100 = 12 - 0111 = 7 If either value falls between 10 - 15, replace that with the corresponding letter. - 12 --> C Combine the two values in the proper order to get the hexadecimal value. - 11000111 = C7

converting binary to decimal

1. Line up the binary values with the powers of 2. 2. Bring down the matching decimal value for each 1 in the binary value. 3. Ignore any 0. 4. Add the decimal values together.

converting decimal to binary

1. Subtract the highest power of 2 from the decimal value until 0 is reached. 2. For every power of 2 that can be subtracted, a 1 is put in that place. If a power of 2 cannot be subtracted, a 0 is put in its place.

loopback address

127.0.0.1 This special address is also known as home or localhost. This address is reserved by each network interface card (NIC) and is used for testing purposes.Ping requests can be sent to this address and if returned means that the NIC is capable of sending and receiving data packets.

Automatic Private IP Addressing (APIPA)

169.254.0.0 A feature that allows a device to automatically assign itself an IP address on the 169.254.0.0 network when a DHCP server or manual configuration is unavailable.

nibble

4 bits

subnet mask

A 32-bit number that defines which portion of an IPv4 address identifies the network address and which portion of the address defines the host address.

DHCP exclusion

A feature that excludes pre-set IP address from being handed out through DHCP.

Classless Inter-Domain Routing (CIDR)

A method for allocating IP addresses and for IP routing. CIDR notation is a simplified method of writing a network address with a slash followed by the number of bits in the network ID.

Internet Assigned Numbers Authority (IANA)

A nonprofit, private American corporation that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System, media types, and other Internet Protocol-related symbols and internet numbers.

ANDing process

Accomplished by multiplying each bit of the binary version of the IP address by the corresponding bit of binary version of the subnet mask and calculating the results. Once the results are calculated, they can be converted into decimal notation and the given address is the network ID that the IP address belongs to.

Class B IPv4 Addresses

Address Range: 128.0.0.0 to 191.255.255.255 First Octet Range (Binary): 128-191 (10000000-10111111) Subnet Mask: 255.255.0.0 Number of Addresses: 65,536 (2^26) Private Reserved IP Range: 172.16.0.0 - 172.31.255.255

Class C IPv4 Addresses

Address Range: 192.0.0.0 to 223.255.255.255 First Octet Range (Binary): 192-223 (11000000-11011111) Subnet Mask: 225.225.225.0 Number of Addresses: 256 (2^8) Private Reserved IP Range: 192.168.0.0 - 192.168.255.255

Class D IPv4 Addresses

Address Range: 224.0.0.0 to 239.255.255.255 First Octet Range (Binary): 224-239 (11100000-11101111) Subnet Mask: N/A Number of Addresses: N/A Private Reserved IP Range: Used for multicast

Class E IPv4 Addresses

Address Range: 240.0.0.0 to 255.255.255.255 First Octet Range (Binary): 240-255 (11110000-11111111) Subnet Mask: N/A Number of Addresses: N/A Private Reserved IP Range: Experimental / Research

DHCP assignment

Admin configures a DHCP server with the IP addressing information such as the IP addresses, DNS server, default gateway, subnet mask, etc. The DHCP server assigns the IP information to the clients base don that configuration. This ensures that each device is assigned a unique IP address.

octet

An 8-bit binary number. An IPv4 address consists of four octets separated by a dot.

DHCP reservation

An IP address that is set aside by a DHCP server for a specific network client (host), which is identified by its MAC address.

private IP

An IP address that is used only on an internal network. These IP addresses do not go out on the internet.

public IP

An IP address that is used to access the internet.

special IPv4 addresses

Automatic Private IP Addressing (APIPA) 169.254.0.0 Loopback 127.0.0.1 Network *.*.*.0 Broadcast *.*.*.255 Note: Because the Network address and Broadcast address reserve the first and last valid IP addresses, no host ID can end in a 0 or 255. The first useable or assignable IP address is .1 and the last useable or assignable is .254 for a Class C subnet.

hexadecimal numbering system

Base-16 numbering system consisting of decimal numbers 0-9 and letters to represent values 10-15. A = 10 B = 11 C = 12 D = 13 E = 14 F = 15 Word is a combination of the Latin prefix hex for 6 and decim for 10. Values combine letters and numbers to simplify or shorten longer binary numbers. Each value is equal to a nibble (four bits).

IP address regulation

Because IP addresses assigned to hosts must be unique, the use of IP addresses on the internet is controlled by organizations that ensure that every organization is given its own range of IP addresses to assign to hosts. The Internet Assigned Numbers Authority (IANA) manages the assignment of IP addresses on the internet. IANA is operated by the Internet Corporation for Assigned Names and Numbers (ICANN). IANA allocates blocks of IP addresses to Regional Internet Registries (RIRs). An RIR has authority over IP addresses in a specific region of the world. An RIR assigns blocks of addresses to Internet Service Providers (ISPs). An ISP assigns one or more IP addresses to individual computers or organizations connecting to the internet.

fixed-length subnet mask (FLSM) method

Bits are borrowed from the host ID and added to the network ID in IP addressing. First, determine how many bits are borrowed form the host portion by using the formula 2^x, where x = the number of bits borrowed. When bits are moved from the host ID to the network ID, the number of subnets is determined by the possible combinations of 1's and 0's of the borrowed bits. When subnetting, the number of hosts per subnet is reduced. To calculate the number of hosts per subnet, use the following formula: 2^y -2, where y = the number of bits in the host ID. Two addresses are subtracted because the first IP in each subnet is the reserved network address and the last IP is for the broadcast address. Using this method, each subnet has the same number of hosts. FLSM is typically used in private networks as it requires less configuration and administration.

IPv4 addres format

Consists of 4 decimal numbers separated by a dot. Each place in the address is know as an octet because it consists of an 8-bit value. Can be represented in two ways, decimal or binary. Most commonly written in decimal notation, where each octet must be between 0 and 255.

Each IP class has a reserved range for private IP addresses due to two factors:

Each IP address on any network, including the internet, must be unique. There is a finite number of IP addresses using IPv4.

Find the Network ID and Host ID given: IP Address: 192.168.5.24 Subnet Mask: 255.255.255.0

Find the IP Address and Subnet Mask given: Nework ID: 192.168.5.0 Host ID: .42

IPv4 Address Classes

IP addresses have a default class. The address class identifies the range of IP addresses and the default subnet mask used for the range. Each IP class has a reserved range for private IP addresses.

public IP addresses

IP addresses used on the internet Typically assigned by the ISP.

private IP addresses

IP addresses used only on internal networks and not on the internet. When a device on the internal network accesses the internet, that data traffic is sent using the public IP address of the network. Because these addresses are never used on the internet, users in one private network of a company can have the same IP addresses as users in the private network in another company.

static assignment

IP information is manually configured on each host. Best used in: - Networks with a small number of hosts. - Networks that do not change devices often. - Devices that must always have the same address (e.g., servers, printers, and routers). You assign permanent addresses to these devices. Challenges include: - Innefficiency: Manually assigning an address means that it is reserved, even if the device is not being used at that time. - Difficult to change: If a server, printer, router, or other device needs a new address, that address must be manually updated on every device that connects to it.

subnet masks

In an IP address, a 32-bit number that identifies the network portion from the host portion of the IPv4 address. In binary notation, it is always a series of 1's followed by a series of 0's. 1's and 0's are never mixed in sequence). The network ID stays the same for all IP addresses in the network, and the host ID changes for each IP address.

IP address

Layer 3 logical address that identifies and locates each device on a network. Two formats, v4 and v6.

decimal numbering system

Most used number system across the world. Base-10 numbering system, which means every place in a number is a power of ten. Comes from the latin rot word decim, which means ten. Consists of ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. All decimal numbers can be calculated using powers of ten to generate larger numbers. Example: 6,789 = (6 × 10³) + (7 × 10²) + (8 × 10^1) + (9 × 10^0) = 6,000 + 700 + 80 + 9 = 6,789

binary numbering system

Number system that computers and most electronic systems use. Base-2 numbering system uses only 2 numbers, 1 and 0. Values of on/off, true/false. Expressed in powers of two. In networking, 8-bit binary numbers are used most often.

Class A IPv4 Addresses

Range: 1.0.0.0 to 126.255.255.255 First Octet Range (Binary): 1-126 (00000001-01111110) Subnet Mask: 255.0.0.0 Number of Addresses: 16,777,216 (2^24) Private Reserved IP Range: 10.0.0.1 - 10.255.255.255

converting hexadecimal to binary

Same process as converting decimal to binary. The only difference is any latter must be converted to it's decimal equivalent first. Each decimal value is then converted to the 4-bit binary value. Example: Convert DF into binary. Convert each letter to its decimal value. - D = 13 - F = 15 Convert each decimal to binary. - 13 = 1101 - 15 = 1111 Combine the binary strings in the proper order to get the binary conversion. - DF = 11011111

fixed-length subnet mask (FLSM)

Subnetting method in which each created subnet has an equal number of addresses.

variable-length subnet mask (VLSM)

Subnetting method in which each subnet can be a different size.

variable-length subnet mask (VLSM) method

Subnetting method used to create subnets of different sizes to reduce IP waste. First step is to create a table showing the different subnets and possible host addresses: CIDR Notation/Hosts per Subnet /24 = 245 /25 = 126 /26 = 62 /27 = 30 /28 = 14 /29 = 6 /30 = 2 The second step is to list the needed subnets ranked from the most addresses needed down to least number needed. Each subned is then assigned the network address that will provide the needed addresses with minimal waste. Keep in mind that for this method to work, the network must be using advanced routing protocols such as OSPF, BGP, and others. This method is typically used by ISP's and larger public networks as it requires complex configuration.

interesting octet

The first octet whose subnet mask is not 255. It is the octet that bits are borrowed from and where the host ID starts.

2^x x = number of bits borrowed

The formula used in the first step of subnetting in order to determine how many bits are borrowed from the host portion.

2^y - 2 y = number of bits in the host ID

The formula used to calculate the number of hosts per subnet. Two addresses are subtracted because the first IP in each subnet is the reserved network address and the last IP is reserved for the broadcast address.

supernetting

The process of combining two or more networks. Requires the networks to be in sequence, otherwise they cannot be combined. When routers talk to each other, they share their routing tables. As networks become more complex, these routing tables can get quite large and complicated. This process combines several subnets and reduces the number of entries in a routing table.

subnetting

The process of dividing a large network into smaller networks called subnets.

ANDing

The process used to determine the network address/ID.

DHCP scope

The range of IP addresses a DHCP server can assign to hosts.

DHCP Process

When a DHCP client system boots, it contacts the DHCP server for IP configuration information. Scopes are the range of IP addresses it can assign to hosts. - The DHCP server can be configured to prevent specific addresses in the range from being assigned to clients. This is called exclusion. - The DHCP server can also be configured to deliver the same address to a specific host each time it requests an address. This is called a reservation. The DHCP server can also be configured to assign other IP configuration information, such as a default gateway and DNS server addresses. The DHCP server assigns the IP address and other information to the client. The assignment is called a lease, and includes a lease time that identifies how long the client can use the IP address. - Periodically, the client contacts the DHCP server to renew the lease on. the IP address. The client will also attempt to renew the lease on the same IP address if it reboots. - The DHCP lease process uses broadcast frams at Layer 2. By default, DHCP broadcasts between subnets enable IP helper or DHCP relay on the appropriate routers. - When the lease expires, the DHCP server releases the reserved IP address. This is known as the expired IP address. Any client configured to use DHCP can get an IP address from any server configured for DHPC, regardless of its operating system.