What is Public and Private IP Address?
One of the biggest challenges with IP version 4 (IPv4) addresses is that we’re running out of them. Simply, these are not enough IP version 4 addresses used to go around to everybody in the world that needs an IP address. IP version 6 (IPv6) is going to be coming to rescue. However, we still have a big IP version 4 deployment out there. And what are a lot of companies have done they said well for my service providers. We know they’re not going to be able to give me five hundred or five thousand IP addresses that we need for my internal use. So one we’ll do instead uses a private range of ipv4 addresses. We can route inside of a company using plenty of these private IP addresses. But these private IP addresses it needs to be translated into a publicly routable IP address. The public and private IP address are always required NAT to translate between each other.
We can have a several like IP address translated into the same publicly routable IP address. Think about in our home if we have a wireless router connected to our cable modem or connected to the DSL. We might have a laptop or we might have a tablet, a Smartphone, and a desktop all connected out to the internet at the same time. Maybe a gaming console as well but our service provider has only given you one publicly routable IP address. What’s happening inside of that wireless router? There is something called a network address translation where we can translate between this non-routable pool of private IP address to one or more IP addresses that are publicly routable. We just need at that time to understand that there are certain ranges of IP addresses better for use inside our company or inside our home. Their private IP addresses these are not going to be routable on the public internet.
Public and Private IP Address:
In addition, we’ve got ranges of IP addresses for classes ‘A’,’B’ and ‘C’ are usually known as IP address classes. Let’s take a look at the each one of these IP address classes. Many people use gravitate towards the 10.0.0.0 address space. Because there are so many addresses available in the 10.0.0.0 address space. We’ve got twenty-four (24) bits that we could use to assign the host that’s over sixteen million IP addresses. So many people just to use that 10 address space inside the company. Then translate that into one or more publicly routable IP addresses. In class ‘B’ IP address classes or address range, we’ve got 172.16.0.0/16.
Therefore, many people use that one that literally common on a lot of wireless routers out there. They all use a class ‘C’ private IP address and there are plenty too big from. We start with 192-168 and we can play with the rest of the bits to make up our own internal address subnets and the host addresses. These are addresses that we’ve talked about this for the 10 address space and the 172 address space. By the way in the 172 address spaces notice the second octet. Lots of people miss this the second octet does not have to be 16. It can go all the way through 31 so, it’s 172.16.0.0 all the way through 172.31.255.255. We talked about the 192.168.0.0 address spaces well what did we skip over the 169.254.0.0/16 address space.
Non-Routable Private IP Ranges:
Well out of all of these private IP address ranges that 169.254.0.0/16 address space. It is not routable even inside our organization. It is not routable even by the router that we own. Generally, we do not want our host that to have an IP address in this range. What is this? It is a self-assigned address. A device in our network wanted an IP address but we didn’t manually assign one. It didn’t dynamically learn one from an address server. Like DHCP (dynamic host configuration protocol) server. So, what we do it just self-assigned an address to itself so it could speak IP. This is generally an indication that something has failed. This host needs attention, it needs an IP address that is routable IP address in this range are known as APIPA addresses.
However, the thing takes away from this article is that we have ranges of private IP addresses. IP addresses that are not going to be routable on the public internet. We could use those inside of our company and then translate those into a routable IP address. That we get from our internet servers provider. But be cautious of that one address space 169.254.0.0/16, that range generally indicates a failure. That’s a self-assigned address and it’s not routable even within our private network. These are the big differences between public and private IP address.
- Network Translation Address (NAT) translates between public and private IP address.
- Private IP addresses are not routable on the public internet.
- Dynamic Host Configuration Protocol (DHCP) is a protocol used to assign an IP address to network devices.
- Automatic Private IP Addressing (APIPA) is non-routable addressing assigned to a host that did not have an IP address manually or dynamically assigned.
- Private IP addresses are the ranges of IPv4 addresses that could be used inside a company but are not routable on the public internet.
- 169.254.0.0/16 is a range of private IPv4 addresses that are used for APIPA addressing and are not routable, even within a private network.