IP addresses – what are they and what do they do?

What is an IP address?

Internet Protocol (IP) addresses function a lot like real-world home or return addresses on mail. A computer or laptop is assigned one by an Internet Service Provider (ISP) through the router.

More specifically, each device accessing the internet through your router will be assigned its own local IP address. But, on the internet, each of the devices will display the same online IP address.

How does it work?

Like a home address, the receiver of your information uses it to send information back to you. Your login details are ‘mailed’ to a website, the website checks this information and sends the relevant information (a successful or failed login in this instance) back to your IP address, and this information is received on your PC or laptop. If multiple PCs or laptops access your home internet, the router uses your device’s local IP address to get information back to you and not another device accessing the internet through the same modem.

Types of IP address?

Two types of IP address exist: static and dynamic.

A static IP address is manually configured by editing a computer’s network settings. This is the rarer of the two and can create network issues if done without a keen knowledge of Internet Protocol.

Dynamic addresses are far more common. The Dynamic Host Configuration Protocol (DHCP), a service running on your home network, assigns them. A DHCP is most commonly run on network hardware such as a router or a dedicated DHCP server. The router assigns local and internet IP addresses in most households.

Everyday usage

Whether sending an E-Mail, logging-in to a website or entering payment and shipping details, information requests need to be sent to and received by the right destination. IP addresses make this happen.

Since ISPs give access to the Internet, it is their role to assign IP addresses to computers. Every information and access request is sent through them, and they know to route it back to you specifically by using your IP address.

IP addresses differ from a home address in some ways though. It can change, unlike a home address. Something as simple as turning a modem or router on and off can change it. Your ISP can also change it for you upon request.

It stays at home

Much like your home address, you don’t take your IP address around with you. If you check your IP address at home, it will (mostly) stay the same; hop on Wi-Fi at your local coffee shop and you’ll notice that it is different.

Furthermore, unlike where your IP address will normally stay the same at home, it will likely be different at the coffee shop each time. This is because public Wi-Fi systems assign a random, non-unique, temporary IP address to a user each time they access it. Once you’ve left the coffee shop, your laptop leaves that IP address with it.

IP addresses and websites

Every domain has an IP address assigned to it. However, these are usually not unique. Fully Qualified Domain Names (FQDNs) were developed as a means for web hosting servers to handle the ever-increasing number of websites in need of a unique address.

Aside from FQDNs, there are dedicated IP addresses which are unique and assigned exclusively to a single hosting account. Shared hosting accounts share a server’s IP address and cannot have a dedicated IP.

For instance: www.example.com, random.org and infinitum.net could all be on a shared hosting account, sharing the same IP address 123.45.67.89 – it is their FQDN that points visitors toward their website. However, large amounts of traffic to www.example.com and random.org can negatively affect infinitum.net’s user speed. This is due to so much traffic on the shared IP address.

This is where dedicated IP addresses come in handy. Only your FQDN uses that IP address – they are complete unique. This means traffic on other websites can never influence yours. A dedicated IP address also lets people visit your website by typing it into the search bar, instead of the FQDN. However, this isn’t a particularly useful feature as FQDNs are easier to memorize and type than IP addresses.

IP and SSL

SSL Certificates were once able to be issued to IP addresses. A Certificate Authority Browser Forum (CA/B Forum) guideline effective from October 1^st 2016 saw this practice banned by all trusted CAs. This is because, as previously mentioned, non-dedicated IP addresses are not unique. Thus, a person could have a CA issue them a copy Certificate of one and use it for intercepting transmissions.

It was also once the case that a website needed a dedicated IP in order to install an SSL Certificate. This is no longer the case – a website’s IP address could change 100 times in a day without affecting its SSL Certificate. Nowadays, all that is required to get an SSL Certificate is an FQDN.