All language subtitles for 11. RFC1918 - Class A, B, C and IPv4 Link Local Addresses

So once again or if see 19:18 discusses IP addresses that are not readable on the Internet they are

three blocks of addresses one class a network 16 Class B networks and 256 class C networks.

You know the range of addresses once again.

And remember when you are sending traffic internally from an IP address such as 10.0 1.1 that one to

a web site such as Google dot com or Facebook does come your IP address has to be netted or network

address translated to a public IP address such as 15 at 1.1 one.

This is a public class A address and this is a private plus a address these addresses will not be accepted

by Internet service providers and therefore will not be routed onto the internet unless of course an

Internet service provider forgot to add an access list to blocking traffic from these networks.

So in this example my PC has an IP address of 10.0 deserted at six.

That is a private IP address which is not a ratable on the internet but I am able to ping yahoo dot

com which has a public IP address of 87 or 2 4 8 dot 122 dot 122.

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

traffic to the Internet.

Here's another example ping Google dot com.

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

That is not covered in this video.

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

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

a router.

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

the internet.

My address is being enacted when I traverse my local internet gateway which can be as simple as your

router at home which connects you to the Internet the next special IP address range is the IP version

for link local addresses or more formally dynamic configuration of IP version 4 link local addresses

as per RAFC 3 9 to 7.

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

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

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

servers are available.

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

in the range 1 6 9 or 2 5 4 0 0.

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

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

you had to either allocate an address using DHP or you had to manually configure the IP addresses on

the PCs to communicate with each other these days.

That's not necessary because IP version 4 link local addresses will allow two computers to communicate

with each other when no DHP server is available.

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

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

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

randomly generate the host specific portion of the address.

This is a Class B address.

Notice the mosque to find 5.4 5.0 zero which indicates that the first two octets sees a network and

hosts will randomly choose the host specific portion of the address.

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

two devices together without the need of a DHP server allocating addresses the two PCs can immediately

communicate with one another.

The user doesn't have to configure ADHD be server or manually configure IP addresses on the PCs.

As long as the two PCs are connected via a cable or a local segment through a switch as an example they

can communicate using IP.

So a PC with IP address 1 6 9 to 5 for that one can communicate with another PC which for example chose

an IP address of 1 6 9 2 5 4 1 2 2 no manual configuration is required in this example I'm using consecutive

addresses but typically the addresses chosen by the hosts are random and won't be sequential like in

this example.

Be careful however with those address range.

It's not readable.

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

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

link but they will not be able to communicate with devices on the Internet or devices in a different

subnet.

So if you type IP config on a PC for example and you see that the PC has an address in the range 169

are too far for Dot XRX.

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

version for link local address.

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

It simply chose an address from the 169 to 5:4 address range.