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Some books say IP address is used to identify the host. Some YouTube videos say that IP address is used to locate the device. It tells us which network the device is located at but it is the mac address that identifies the device

Does IP address locate the device? Or does it identify the device? From what I know, the IP address can change. Only mac address is fixed.

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    An IP or MAC address may be used to identify a device. Strictly speaking, they just identify an interface. 'Identify a device/interface' also has several perspectives, from application layer (FQDN) to network layer (IP address) to link layer (MAC address).
    – Zac67
    Oct 20, 2022 at 13:20

2 Answers 2

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Both can be true because they are identifying the host at different network layers.

Remember that not all data-link protocols use MAC addressing. The data-link protocol may use addressing to identify a host on a LAN (not all data-link protocols even have addressing; PPP only links two devices, so there is no need for an address because any frame is destined to the only other host on the LAN). Data-link protocols encapsulate the network layer packets inside data-link frames.

IP addressing identifies a device at the network layer, and it is also used to route packets between networks to a distant host. The packets that travel between networks will be encapsulated and decapsulated with the various data-link protocols in between the source and destination hosts. Not all packets are destined for a distant host, and they can identify a host on the LAN, but either way, the packets get encapsulated inside frames for delivery on the LAN.

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    Sorry @Effie, both is a plural indefinite pronoun. So are is correct.
    – Ron Trunk
    Oct 20, 2022 at 12:40
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    @Effie, I wrote can because not all data-link protocols use MAC addressing. On a data-link protocols that uses MAC addressing, both are true, but with something like frame relay or ATM, there is no MAC addressing, so both are not true because there is no MAC addressing.
    – Ron Maupin
    Oct 20, 2022 at 12:48
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    Not a good analogy.
    – Ron Maupin
    Oct 20, 2022 at 14:34
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    Well, if it is on the Internet, it must be true - not.
    – Ron Maupin
    Oct 20, 2022 at 15:08
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    sorry, this video is really bad. you need to understand the concept of local networks, aka layer 2, and Internet(working) aka layer 3 which connects different local networks into Internet. Each local network can have its own addressing scheme, which is used to forward packets between devices on the same network. Internet interconnects all local networks into one global network. This global network uses its own addressing scheme, the IP addresses, each of which identifies a device, connected to the network.
    – Effie
    Oct 20, 2022 at 15:32
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so my question is does ip address locate the device or does it identifies the device because from what i know the ip address can change and only mac address is fixed

Adding a bit about IP as an identifier… in some cases IP subnets can be duplicated in different routing tables or VRFs… as such IP isn’t a good identifier. Use dot1x if you need to establish identity…. Mac addresses / IP addresses can easily be spoofed if you are not requiring bidirectional traffic in the identification process.

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