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IP Networking Transcription

Welcome to our IP networking module. In this module, we will discuss IP version 4 and IP version 6. Internet protocol version 4 or IPv4 is a layer three protocol that is designed to route wide area network data. It is considered a connectionless protocol and is unreliable because it does not ensure that packets arrive in the correct order.

And also does not ensure that packets are undamaged. IP packets have a header which includes all of the necessary information that a router needs to be able to forward the packet to its intended destination IP version 4 uses 32 bit IP addresses which can be either shown as decimal or binary.

IP addresses involve four groups of numbers separated by three periods. IP addresses are also used with a subnet mask, which is responsible for finding the network portion of the address, which is the left-hand portion and the host portion of an IP address, which would be the right-hand portion.

And this is needed for routers to be able to route data appropriately. For example, the IP address we see on the screen here, 192.168.1.5 with a subnet mask of 255.255.255.0, would indicate that the first three octets or groups of numbers in the IP address would dictate the network portion of the address.

In this example, 192.168.1 would define the network itself. And the last octet or the .5 would define the specific computer on the 192.168.1 network. 255.255.255.0 is a common subnet mask used in many home networks and small office networks, and this can be shown as /24 with C-I-D-R or cider, which stands for classless inter-domain routing.

The slider is used to make it easier, rather than writing out the entire sub net mask, the user can use a slash notation. Port numbers are added as an extension to the end of IP addresses, with a colon separating the IP address from the port number. When IP Version 4 was originally created, classes of network addresses were defined Class A involved IP addresses with the first octet from 0 to 126.

IP addresses starting with 127 are reserved for loop back and are not used. The IP addresses in Class A had a subnet mask of 255.0.0.0 or /8 with CIDR notation. With Class B addresses, this involved IP addresses with the first octet staring with 128 through 191, and in a Class B network the subnet mask is 255.255.0.0, or /16, which indicates that the first two bytes, or octets, are used to define the network.

Class C addresses involve IP addresses with the first octet between 192 and 223, with a subnet mask of 255.255.255.0 or /24. Here, the first three bytes are used to define the network. Class D IP addresses start with 224 and range through 239, and this is used for multi cast traffic and class E was for experimental IP addresses that are never used on the Internet and these range with a first octet of 240 through 255.

For the CISSP examination you should remember that 127.0.0.1 is the loopback address, and IP addresses starting with 127 are not valid on the internet. IP version 4 addresses always have two parts. The left portion of the IP address identifies the network and this would be the same for all computers on that network.

The right portion of the IP address would be unique to each system and identifies the individual host. The subnet mask shows where the break is between the identification of the network and the host itself. If you look at the zeros in the subnet mask, this will tell you how many hosts are included on that network.

For example, with a class b address two five five dot two five five dot zero dot zero is the subnet mask. And because there are two sub-octets of zero, this means that you could have any combination of 256 numbers in either of those octets so we would take 256 times 256 and we would come up with a total possibility of 65,530 hosts on a class B network.

When we look at a class C network, 255.255.255.0 Is the subnet mask. And because we only have only one octet of zero, we have 256 possible hosts. Whenever you subtract a bit from the subnet mask, you will double the total number of hosts on that network. If you add a bit to the subnet mask, there will be half the hosts on that network.

And this is an easy way to calculate the number of hosts on a network based on the subnet mask. There are a total of 4.3 billion IP version 4 addresses that are able to be assigned. Because of the fact that we have so many devices and because these IP addresses were not assigned cautiously, we have run out of IP version 4 addresses, causing the introduction IPv6, which is also a layer three protocol.

Instead of using 32 bit addresses, IPv6 uses 128 bit IP addresses. And here we have eight blocks of four hexadecimal digits. Separated by colons instead of being separated by dots. Unicast IP version six addresses are split into two equal parts. The 64-bit network on the left and the 64-bit host is identified on the right.

So with IP version six, we do not have a subnet mask like we did with IP version four. All IP version six IP addresses will have this split between the network and the host identifier at the same position. In order to shorten IP version six addresses, you can eliminate leading zeroes.

For example, we can see the second IP address on the screen here 2113: DC2:2F29 etc. Is the same IP address that is listed a little bit higher up on the slide, but all of the leading zeros have been eliminated making the IP address much easier to write. If you have adjacent blocks of nothing but zeros, you can also replace these blocks with the double colon. This is known as zero compression, but you can only do this one time, so we can see the IP address at the bottom 21.13: DC2:2F29::3D:9C5A, is exactly the same as the IP addresses above it. We have just removed the zeroes in order to make the IP address shorter and easier to write.

Global addresses are basically public addresses that are globally reachable on the Internet. With global addresses the first 48 bits of the address are the global routing prefix, and the next 16 bits are the subnet ID. This allows up to 65,536 different subnets. If you plan on using IP version 6 in your local area network, you can use link local addressing, which is is similar to APIPA, or automatic private IP addressing.

This allows devices to self-assign non-routable local IP addresses in order to communicate on the local subnet. These IP addresses can be easily recognized because they will always begin with fe80::, which is the equivalent of fe80:0:0:0. In order to differentiate between different network segments A zone ID can be added to the end of the IP address after the percentage symbol.

IP version six tunnels can be used to take IP version 6 traffic, and move it over IP version 4 networks that may not be compatible with IP version 6. However, these tunnels can be misused by attackers. For the CISSP examination, you should remember that attackers can use IP version 6 tunnels in order to bypass security controls or launch attacks on your network.

This concludes our IP networking module. Thank you for watching.