IPv4 - 220-801

Two Parts of an IP Address

A IPv4 address has two parts. The first part is the network identifier, or network ID, and the second part is the host identifier, or host ID.

Private IP Address Class A

10.0.0.0 - 10.255.255.255

IPv4 Primary Type Of Addressing - Multicast

Multicast is one-to-many traffic. A system can send data to multiple other systems. Multicast addresses are in the range of 224.0.0.1 through 255.255.255.254. Multicast traffic is routed to the correct destination through one or more routers.

Network Identifier, or Network ID

The first part of an IP address. The network ID identifies the network. All computers within a network must have the same network identifier.

Host Identifier, or Host ID

The second part of an IP address. All computers within a network must have different host identifiers. More specifically, no two systems can have the same IP address. Because the network IDs must be the same, the host IDs must be different on the network.

TCP/IP

Transmission Control Protocol (TCP) and the Internet Protocol (IP)

WINS Server

WINS resolves NetBIOS names to IP addresses

Loopback Addresses

127.0.0.0 through 127.255.255.255 is reserved for testing. However, there's really only one address used in this range for testing. It's called the loopback address, and the address is 127.0.0.1.

Private IP Address Class B

172.16.0.0 - 172.31.255.255

Private IP Address Class C

192.168.0.0 - 192.168.255.255

Three Most Common Subnet Mask

255.0.0.0 255.255.0.0 255.255.255.0

DNS Server

DNS resolves host names to IP addresses

IPv4 Primary Type Of Addressing - Unicast

Unicast is one-to-one traffic. That is, the data is sent from one system to one other system. Unicast traffic is routed to the correct destination through one or more routers.

IPv4 Addresses

IPv4 addresses are created with 32 bits. IPv4 addresses are commonly displayed in dotted decimal format because it's not easy for us to read a string of 32 ones and zeros.So Each IP address has four decimal numbers separated by three dots, like this: 192.168.1.5. Each decimal can be represented with eight bits (also called an octet). Four octets (or four sets of eight) add up to 32 bits. If all bits are a one in any octet (1111 1111), the value is 255. This is important to remember because an IPv4 address cannot have any decimals greater than 255. IPv4 uses three primary types of addressing when sending traffic. The types are unicast, broadcast, and multicast.

IP Conflicts and 0.0.0.0

If two systems have the same IP address, it results in an IP address conflict. Usually, one system will recognize the conflict and assign itself an IP address of 0.0.0.0 and will be unable to communicate on the network. In some cases, both systems will be unable to communicate on the network.

Gateway

A gateway is a path out of a network, and the default gateway identifies the default path out of a network. For example, if an internal system is trying to connect to the Internet, it goes through the default gateway. The default gateway is an interface on a router, and it has an IP address. When a system transfers traffic from one computer to another, it first identifies the network ID of both systems. If the network IDs are the same, it knows that the computers are on the same network. If the networks IDS are different, it knows it needs to go through the default gateway

Subnetworks, or Subnets

A subnet allows the flow of network traffic between hosts to be segregated based on a network configuration. By organizing hosts into logical groups, subnetting can improve network security and performance.

Subnet Mask

A subnet mask is a number that defines a range of IP addresses that can be used in a network. Subnet masks are used to designate subnetworks, or subnets, which are typically local networks LANs that are connected to the Internet. Systems within the same subnet can communicate directly with each other, while systems on different subnets must communicate through a router. Therefore, subnetworks can be used to partition multiple networks and limit the traffic between them. A subnet mask hides, or "masks," the network part of a system's IP address and leaves only the host part as the machine identifier.

APIPA Addresses

APIPA addresses are assigned if a DHCP client does not receive a response from DHCP. They always start with 169.254 and have a subnet mask of 255.255.0.0. They never assign a default gateway, address of a DNS server, or any other information. If you see an APIPA address, it's a clear indication of a DHCP-related problem. Troubleshooting steps would include identifying why the client can't reach DHCP and why DHCP is not responding.

Classful IP Address

Has a predefined subnet mask based on the first number in the IP address. Just by looking at the IP address, you can identify the subnet mask. When you know the subnet mask, you should also be able to identify the network ID.

Octet

An octet is a unit of digital information in computing and telecommunications that consists of eight bits. Octets are used in the representation of Internet Protocol computer network addresses. An IPv4 address consist of four octets, usually shown individually as a series of decimal values ranging from 0 to 255, each separated by a dot.

IPv4 Primary Type Of Addressing - Broadcast

Broadcast is one-to-all traffic. One system sends the data to all other systems on the network. However, this is certainly not to all other systems in the world. Routers block broadcast traffic so that a broadcast is sent only to all the computers with the same network ID. A broadcast address is 255.255.255.255. Only broadcast traffic stops at routers

CIDR Notation (Classless Inter-Domain Routing Notation)

CIDR notation identifies the number of bits that are one in the subnet mask, using /n. In this case, the n is the number of bits that are a one.The CIDR number comes from the number of 1's in the subnet mask when converted to binary For example, consider a subnet mask of 255.255.255.0. The first octet is 255, representing eight ones (1111 1111). Similarly, the second octet is another eight ones, and the third octet is another eight ones. Therefore, the first 24 bits of the subnet mask are all ones. In this case, you can use /24 to represent the subnet mask. There is no difference in the actual IP address or subnet mask when CIDR notation is used; it's just displayed differently.

The Subnet Mask and the Network ID

IP addresses are matched with a subnet mask to identify the network ID and the host ID When the subnet mask is 255, that portion of the IP address is the network ID. When the subnet mask is 0, that portion of the IP address is the host ID.

DHCP (Dynamic Host Configuration Protocol)

Dynamic Host Configuration Protocol (DHCP) is used to dynamically assign IP addresses and other TCP/IP configuration information to systems. A DHCP client is any system configured to receive TCP/IP information from a system running DHCP. When a DHCP client turns on, it sends a DHCP query, and if DHCP is running on the network, DHCP will provide TCP/IP configuration to the client. DHCP commonly provides an IP address, subnet mask, and the default gateway. In many cases, DHCP will also provide the system with the address of a DNS server and a WINS server.

Class A IP Address

First Octet Range = 1 - 126 Subnet Mask = 255.0.0.0 CIDR Notation = /8

Class B IP Address

First Octet Range = 128 - 191 Subnet Mask = 255.255.0.0 CIDR Notation = /16

Class C IP Address

First Octet Range = 192 - 223 Subnet Mask = 255.255.255.0 CIDR Notation = /24

NAT (Network Address Translation)

Network Address Translation (NAT) is a protocol that translates private IP addresses to public and public IP addresses back to private. It is installed on a system such as a router or firewall located between the Internet and a private network. Internal networks have private IP addresses and public networks have public IP addresses. However, computers on an internal network still need to be able to communicate on public computers on the Internet. NAT helps this process. It also helps hide internal computers from attackers on the Internet. In smaller networks, a router with NAT would have one public IP address. In many larger networks, devices running NAT use multiple public IP addresses.

Private IP Addresses

Systems on internal networks use private IP addresses, and systems on the Internet use public IP addresses. Private IP addresses are formally defined in Request for Comments (RFC) 1918 as any address in one of the following ranges: 10.0.0.0 - 10.255.255.255 (Class A) 172.16.0.0 - 172.31.255.255 (Class B) 192.168.0.0 - 192.168.255.255 (Class C) These are the only addresses you'll see on any internal network. Additionally, routers on the Internet will not route any traffic using these IP addresses as either a source or destination IP address.