What is an interface address?

That's pretty much my question.

What is an interface address? What is it used for? How is it different from a normal IP address in a network?

I can't seem to find a good explanation/definition on the internet.

This is the best I got : CISCO: what is the interface address?

Solution 1:

An Interface address is an interface (network) address, a network interface address, it's just a network address that belongs to an interface. Though almost all belong to an interface if they're being used. The term you've used brings up an important point.

Almost all network addresses e.g. IP addresses, belong to a network interface. (if they're used at all). Any device with an IP Address, has an IP Address on an interface.

A network interface is the electronics of the part where the network cable connects to - the controller there. Or where the wireless device connects to. NIC stands for network interface controller or network interface (controller) card. WNIC is wireless network interface controller or wireless network interface (controller) card.

IP Addresses belong to network interfaces, not to the computer itself. You don't ping a computer, you ping a computer's network interface.

Even if you ping 127.0.0.1 which is known as the loopback interface. So even that is known as an interface.

A computer could have a NIC with many ethernet sockets, many network interfaces and each one with a different IP Address, see the IP Address belongs to an interface. And electronically, if you ping a computer, you're actually pinging in particular, a or the network interface on the computer.

There aren't many examples of IP Addresses that do not belong to an interface. An IP Address you haven't assigned to an interface (so it isn't assigned to a device, because IPs aren't exactly assigned to devices, only to interfaces of devices).

The network address I suppose does not and even cannot belong to any interface(though I may be wrong on that). And the broadcast address e.g. 255.255.255.255 designed to be sent to all interfaces, no interface would have that address.

Solution 2:

Depending on the context, “interface address” might be used to refer to a MAC address.  An exhaustive discussion of MAC addresses could fill a book, but, in short,

• MAC addresses operate at a lower level of the protocol stack (see also this) than IP addresses,
• MAC addresses are used only for communicating between network interfaces in the same LAN segment, and
• MAC addresses are (typically) (semi-)permanently assigned (often, if you can change the MAC address at all, it has to be done by physically manipulating the network interface hardware), in contrast to IP addresses, which can be mercurial.

Solution 3:

In the case you linked, what is called interface address is the gateway address (the address of the router of the subnet you are connected).

I don't think Interface address can be used with this meaning as I think an interface address is the group of parameters you need to supply to an interface for it to work like:

iface eth0 inet static
    address 192.168.1.180
    netmask 255.255.255.0
    broadcast 192.168.1.255
    network 192.168.1.0
    gateway 192.168.1.1

You can see an example in Juniper routers technical documentation

Solution 4:

Short answer

What is an interface address?

Network interfaces have two addresses:

A layer 2 address - The MAC address (Also called Hardware , physical or burned-in address).

A layer 3 address - The IP address (version 4 or 6).

What is it used for?

Both addresses are used in order to communicate between network devices.

MAC address - to uniquely identify every node (e.g., workstations and printers) on a network.

IP Address - used in order to communicate with a device on a network, or between different networks.

How is it different from a normal IP address in a network?

By ‘normal’ IP address you probably mean the gateway (router) external IP - this is what you will see if you’ll search “what is my IP address” in Google.
If you didn’t mean the router - so the normal IP addresses are probably the network interface IPs.

Some more information:

A MAC address is a six-byte identifying number which is permanently embedded in the firmware of the adapter. It is readable by the network and the OS of the device on which the adapter is installed. Every adapter has a unique MAC address.
Because MAC addresses never change, they are very useful on preventing unwanted network access by hackers and intruders. Read more about MAC filtering.

The IP address of network interface is in most cases a dynamic, private IP address which was given to the network interface by the DHCP (server or router).

If device A and device B are on the same network, and the MAC address of device B is known by device A - they can communicate directly based on the MAC address.

If the two devices are on different networks, they will have to go through a router and the communication is done one level up in the TCP/IP model and will be based on the IP addresses.

The mapping between the IP and MAC address is done by the ARP protocol.