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So once again or if C 1918 discusses IP addresses that are not readable on the internet, they are three

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blocks of addresses, one class A network, 16 Class B networks and 256 Class C Networks.

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Here are the range of addresses once again.

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And remember when you are sending traffic internally from an IP address such as 10.1 1.1 to a website

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such as google.com or Facebook.com, your IP address has to be netted or network address translated

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to a public IP address such as 15.1 1.1.

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This is a public class A address, and this is a private class A address.

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These addresses will not be accepted by Internet service providers and therefore will not be routed

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onto the Internet unless, of course, an Internet service provider forgot to add an access list.

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Blocking traffic from these networks.

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So in this example, my PC has an IP address of 10.0 0.6.

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That is a private IP address, which is not readable on the Internet.

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But I am able to ping yahoo.com, which has a public IP address of 87.2, 48.1, 22.1 22.

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And that's because my IP address is being netted or network address translated by my router when I send

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traffic to the internet.

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Here's another example.

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Ping Google.com.

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The pings succeed because once again my IP address is being netted.

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Nat is not covered in this video.

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Please refer to other videos for explanations of network address translation.

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But in brief, Nat will translate one of these IP addresses to a publicly readable address when traversing

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a router.

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That's how I'm able to use a private IP address on my local PC, but still be able to access devices

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on the internet.

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My address is being noted when I traverse my local internet gateway, which could be as simple as your

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router at home, which connects you to the internet.

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The next special IP address range is the IP version for link local addresses or more formally dynamic

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configuration of IP version for link local addresses as per or FC 3927.

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Microsoft referred to this address order configuration method as automatic private IP address or API

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pay.

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So that's Microsoft IP version for link local addresses.

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Now this is used where a PC is configured for DHCP or dynamic host configuration protocol, but no DHCP

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servers are available.

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So an IP address cannot be allocated via DHCP and therefore the PC automatically chooses an IP address

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in the range.

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169.254.0.0.

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This allows computers to use link local IP addresses for communication on a local segment.

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Now, in the really, really old days of networking, going back to Windows 3.1, if you wanted to PCs

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to communicate, you had to either allocate an address using DHCP or you had to manually configure the

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IP addresses on the PCs to communicate with each other.

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These days, that's not necessary because IP version four Link local addresses will allow two computers

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to communicate with each other when no DHCP server is available.

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So if you connected to PCs back to back using a cable, they'd be able to communicate with each other

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without the user having to configure static IP addresses on those devices.

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The PCs would simply use an IP address in this range and be able to communicate with each other.

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Hosts randomly generate the host specific portion of the address.

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This is a class B address.

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Notice the mosque 255.255.0.0, which indicates that the first two octets is a network and hosts will

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randomly choose the host specific portion of the address.

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Once again, this makes the lives of non-technical users a lot easier because they can simply connect

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two devices together without the need of a DHCP server allocating addresses.

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The two PCs can immediately communicate with one another.

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The user doesn't have to configure a DHCP server or manually configure IP addresses on the PCs as long

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as the two PCs are connected via a cable or a local segment through a switch.

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As an example, they can communicate using IP.

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So a PC with IP address 16922541.1 can communicate with another PC which for example, chose an IP address

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of 1692541.2.

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No manual configuration is required.

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In this example, I'm using consecutive addresses, but typically the addresses chosen by the hosts

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are random and won't be sequential.

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Like in this example.

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Be careful.

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However, with this address range it's non readable.

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In other words, the hosts can communicate on the local link, but their traffic is non ratable.

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This can cause issues because users will be able to communicate with other devices on the local segment

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or local link, but they will not be able to communicate with the devices on the internet or devices

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in a different subnet.

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So if you type IP config on a PC, for example, and you see that the PC has an address in the range

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160 9.254.6. x.

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That means the PC was not able to get an IP address via DHCP and dynamically allocated itself an IP

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version for link local address.

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No DHCP server was available and thus an IP address wasn't allocated to the device.

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It simply chose an address from the one 6925 for address range.