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 Forum index » Taking the Puppy out for a walk » Misc
Do we need IP address plus MAC address?
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inherit2

Joined: 23 Jun 2014
Posts: 10

PostPosted: Mon 26 Mar 2018, 09:55    Post subject:  Do we need IP address plus MAC address?  

hi,

My question is rather general. I just wonder. Why do we need IP addressing whereas we have MAC addresses. It seems like doing double work. Why hasn't it been possible just to rely on MAC address globally? Why it can't it be that all computers throughout the world are assigned with MAC addresses. Why couldn't we establish sth like MAC-Global-system. Why did internet creators introduced IP addresses.

You live in you home and you have one address, which is globally valid. Be advised that all MAC addresses are unique globally.


thx
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Burn_IT


Joined: 12 Aug 2006
Posts: 3571
Location: Tamworth UK

PostPosted: Mon 26 Mar 2018, 10:33    Post subject:  

That was the original idea - to make every single device have a separate mac address, but unfortunately mass production and in an effort to reduce costs, manufacturers start using generic mac addresses.
Plus spoofing mac addresses is too easy.
IP addresses are not unique either since routers hand out local IP addresses to local devices.

IPV6 should solve that problem, although better control, even of that, is really needed.

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inherit2

Joined: 23 Jun 2014
Posts: 10

PostPosted: Tue 27 Mar 2018, 12:18    Post subject:  

Burn_IT wrote:
, but unfortunately mass production and in an effort to reduce costs, manufacturers start using generic mac addresses.

I am not sure if I get you. generic mac address - what do you mean by that? So is it bad that mac addresses are generic/general?
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Burn_IT


Joined: 12 Aug 2006
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PostPosted: Tue 27 Mar 2018, 12:43    Post subject:  

They made many individual devices of the same design with the same mac address. Every single communication device was supposed to have a different mac address hard coded into it's firmware.
Yes it did matter because every single device was supposed to be identifiable.
As a result there has had to be a new unique scheme devised, IPV6 which gives every device an address.

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inherit2

Joined: 23 Jun 2014
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PostPosted: Tue 27 Mar 2018, 15:32    Post subject:  

Burn_IT wrote:
They made many individual devices of the same design with the same mac address.


I didn't know that. WIKI says about MAC " is a unique identifier assigned to network interface". So if what you say is true, then it is possible that two your computers/NIC have the same MAC addresses. Then you would tear your hair out wondering why your LAN ain't working ...

thanks
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Burn_IT


Joined: 12 Aug 2006
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Location: Tamworth UK

PostPosted: Tue 27 Mar 2018, 16:18    Post subject:  

I've had two PCI cards with the same MAC address. It wasn't a problem as long as they weren't attached to the same router. - though not an ideal situation.
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increa

Joined: 21 May 2011
Posts: 29

PostPosted: Fri 21 Jun 2019, 07:19    Post subject:  

inherit2,

The basic reason is MAC addresses are not routable nor are they translatable. They are fixed (you get only one ...well, unless you're an Apple iPhone spoofing everybody).

IP addresses are necessary at the conceptual level of a network if you want to route data onto/off from private networks. For example, you and I both have home networks running at 192.168.1.x but the IP address is translated to a public IP address going through the cable modem box (or whatever). You can't do this network address translation without the concept of an IP address.

Now.. well.. you ~could~ network address translate MAC addresses if everybody agreed to, but then that would basically be an IP address by another name.
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s243a

Joined: 02 Sep 2014
Posts: 2135

PostPosted: Fri 21 Jun 2019, 12:29    Post subject:  

Burn_IT wrote:
They made many individual devices of the same design with the same mac address. Every single communication device was supposed to have a different mac address hard coded into it's firmware.
Yes it did matter because every single device was supposed to be identifiable.
As a result there has had to be a new unique scheme devised, IPV6 which gives every device an address.


If the MAC address aren't unique then you have to manually configure the IPv6 address:

Quote:

The purpose of this document is to provide an understanding of IPv6 Link-local address in a network. A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are not necessarily bound to the MAC address (configured in a EUI-64 format). Link-local addresses can also be manually configured in the FE80::/10 format using the ipv6 address link-local command.

https://www.cisco.com/c/en/us/support/docs/ip/ip-version-6-ipv6/113328-ipv6-lla.html

Quote:

This link-local IPv6 is infered from the NIC’s mac address.

A mac address is 48 bits, an IPv6 address is 128 bits. Here’s the conversion process step by step:

1. take the mac address: for example 52:74:f2:b1:a8:7f
2. throw ff:fe in the middle: 52:74:f2:ff:fe:b1:a8:7f
3. reformat to IPv6 notation 5274:f2ff:feb1:a87f
4. convert the first octet from hexadecimal to binary: 52 -> 01010010
5. invert the bit at index 6 (counting from 0): 01010010 -> 01010000
6. convert octet back to hexadecimal: 01010000 -> 50
7. replace first octet with newly calculated one: 5074:f2ff:feb1:a87f
8. prepend the link-local prefix: fe80::5074:f2ff:feb1:a87f
9. done!

https://ben.akrin.com/?p=1347

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jafadmin

Joined: 19 Mar 2009
Posts: 957

PostPosted: Fri 21 Jun 2019, 21:31    Post subject: Re: Do we need IP address plus MAC address?  

inherit2 wrote:
hi,

My question is rather general. I just wonder. Why do we need IP addressing whereas we have MAC addresses. It seems like doing double work. Why hasn't it been possible just to rely on MAC address globally? Why it can't it be that all computers throughout the world are assigned with MAC addresses. Why couldn't we establish sth like MAC-Global-system. Why did internet creators introduced IP addresses.

You live in you home and you have one address, which is globally valid. Be advised that all MAC addresses are unique globally.


thx


They are two physically different things.

MAC addresses are a Layer 2 identifier. Layer 2 handles the physical link state. They are not routable.

IP addresses are a Layer 3 identifier. Layer 3 is the networking layer.
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s243a

Joined: 02 Sep 2014
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PostPosted: Fri 21 Jun 2019, 21:43    Post subject: Re: Do we need IP address plus MAC address?  

jafadmin wrote:
inherit2 wrote:
hi,

My question is rather general. I just wonder. Why do we need IP addressing whereas we have MAC addresses. It seems like doing double work. Why hasn't it been possible just to rely on MAC address globally? Why it can't it be that all computers throughout the world are assigned with MAC addresses. Why couldn't we establish sth like MAC-Global-system. Why did internet creators introduced IP addresses.

You live in you home and you have one address, which is globally valid. Be advised that all MAC addresses are unique globally.


thx


They are two physically different things.

MAC addresses are a Layer 2 identifier. Layer 2 handles the physical link state. They are not routable.

IP addresses are a Layer 3 identifier. Layer 3 is the networking layer.


I wonder if you configure each router port to use a separate subnet if you can get around issues with duplicate arp addresses. Using the router in bridged mode with duplicate arp address might be problematic.

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