Comptia A+ 2.6

Static

A static IP address is an IP address that was manually configured for a device instead of one that was assigned by a DHCP server. It's called static because it doesn't change vs. a dynamic IP address, which does change.In the early days of IP, you had to manually configure everything. You would at an IP address, a subnet mask, a gateway address, the DNS servers, NTP servers, and anything else that needed configuring for your TCP/IP to work properly. All of this changed in October of 1993, and the bootstrap protocol was introduced. We often refer to this as BOOTP. But BOOTP didn't work for everything that we needed to have configured automatically. For example, when we added voice over IP phones to our network, there was no way for BOOTP to add voice over IP gateway information. BOOTP also had no way to know when an IP address was suddenly available again. So we updated BOOTP into a new protocol called dynamic host configuration protocol, or DHCP.

Subnet mask

A subnet mask is used to divide an IP address into two parts. One part identifies the host (computer), the other part identifies the network to which it belongs. To better understand how IP addresses and subnet masks work, look at an IP address and see how it's organized.

VPN

A virtual private network, better known as a VPN, protects your identity and browsing activity from hackers, businesses, government agencies, and other snoops. When connecting to the internet, your data and IP address are hidden by a type of virtual tunnel. This keeps others from spying on your online activity.

APIPA

APIPA stands for Automatic Private IP Addressing (APIPA). It is a feature or characteristic in operating systems (eg. Windows) which enables computers to self-configure an IP address and subnet mask automatically when their DHCP(Dynamic Host Configuration Protocol) server isn't reachable.There are a range of IPv4 addresses assigned just for APIPA. This ranges 169. 254.0.1 through 169.254.255.254. The first and last 256 addresses are reserved, which means if you look at the available IP addresses for workstation, they'll fall in the range from 169.254.1.0 through 169.254.254.255. This means if you turn on a device, and you find you're not able to communicate to the internet, and when you look at the IP addresses, they fall in this particular range, you know you've been assigned an APIPA address.

DHCP

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to automate the process of configuring devices on IP networks, thus allowing them to use network services such as DNS, NTP, and any communication protocol based on UDP or TCP. ... DHCP is an enhancement of an older protocol called BOOTP.

DHCP Dynamic Host Configuration Protocol)

Dynamic Host Configuration Protocol. Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to automate the process of configuring devices on IP networks, thus allowing them to use network services such as DNS, NTP, and any communication protocol based on UDP or TCP.The DHCP process works on a local subnet. But on our network, we have a DHCP server on our local subnet and a DHCP server that is not on our local subnet. To be able to use this DHCP server that's on a different IP subnet than ours, we need to configure our local router to have a DHCP relay address configured. Sometimes, you'll hear this referred to as an IP helper-address. This tells this router that if it ever sees any requests for DHCP, to also send them to this DHCP server that's outside of our local subnet. This means we're now ready for any problems that might occur. If our local DHCP server has a power supply that goes bad and is suddenly unavailable, we can still use this DHCP server that's located elsewhere, because we've configured a DHCP relay.

Reservations

However system administrator may prefer that a device always has the same IP address. For example, they may want a server or a printer to always have the same IP address every day. One way to accomplish this would be to disable DHCP completely on that device. This means you have to manually configure all of the IP address settings. So you as the administrator would have to manually type in the IP address, subnet mask default gateway, DNS settings, and anything else relating to IP. If any of these values need to be changed later you would have to revisit this device and manually reconfigure all of those settings. A much more flexible way to accomplish this will be to create an IP reservation on the DHCP server where you can associate the MAC address of this device to a specific IP address. That way if you need to make changes, you can go to your DHCP server, and those changes will be propagated to all of these devices.

Link local

If you turn on your computer, and you don't receive a response from a DHCP server, you might still be able to communicate with other devices on your network. You're able to do this thanks to automatic private IP addressing, or APIPA. This is what we call a link local address. It's an automatic address that's assigned to your workstation that allows you to communicate on your own IP subnet, but you're not able to communicate outside of your local subnet.

Gateway

In most cases, the default gateway IP address is the private IP address assigned to the router. This is the address that the router uses to communicate with a local home network. Instructions in this article apply to all versions of Windows, including Windows 10 through Windows XP.

NAT

Network Address Translation (NAT) is designed for IP address conservation. It enables private IP networks that use unregistered IP addresses to connect to the Internet. NAT operates on a router, usually connecting two networks together, and translates the private (not globally unique) addresses in the internal network into legal addresses, before packets are forwarded to another network. As part of this capability, NAT can be configured to advertise only one address for the entire network to the outside world. This provides additional security by effectively hiding the entire internal network behind that address. NAT offers the dual functions of security and address conservation and is typically implemented in remote-access environments.

DNS

The Domain Name System (DNS) turns domain names into IP addresses, which browsers use to load internet pages. Every device connected to the internet has its own IP address, which is used by other devices to locate the device.

VLAN

VLANs allow network administrators to automatically limit access to a specified group of users by dividing workstations into different isolated LAN segments. When users move their workstations, administrators don't need to reconfigure the network or change VLAN groups.

Pv4 vs. IPv6

What is IPv4? IPv4 is an IP version widely used to identify devices on a network using an addressing system. It was the first version of IP deployed for production in the ARPANET in 1983. It uses a 32-bit address scheme to store 2^32 addresses which is more than 4 billion addresses. It is considered the primary Internet Protocol and carries 94% of Internet traffic. What is IPv6? IPv6 is the most recent version of the Internet Protocol. This new IP address version is being deployed to fulfill the need for more Internet addresses. It was aimed to resolve issues that are associated with IPv4. With 128-bit address space, it allows 340 undecillion unique address space. IPv6 is also called IPng (Internet Protocol next generation). Internet Engineer Taskforce initiated it in early 1994. The design and development of that suite are now called IPv6. KEY DIFFERENCE IPv4 is 32-Bit IP address whereas IPv6 is a 128-Bit IP address. IPv4 is a numeric addressing method whereas IPv6 is an alphanumeric addressing method. IPv4 binary bits are separated by a dot(.) whereas IPv6 binary bits are separated by a colon(:). IPv4 offers 12 header fields whereas IPv6 offers 8 header fields. IPv4 supports broadcast whereas IPv6 doesn't support broadcast. IPv4 has checksum fields while IPv6 doesn't have checksum fields When we compare IPv4 and IPv6, IPv4 supports VLSM (Variable Length Subnet Mask) whereas IPv6 doesn't support VLSM. IPv4 uses ARP (Address Resolution Protocol) to map to MAC address whereas IPv6 uses NDP (Neighbour Discovery Protocol) to map to MAC address.