I do not understand why this story is being upvoted. Are we supposed to duplicate the answers on serverfault here (which seems to be most of the comments) or are we making fun of the question or what?
Why couldn't MAC addresses be used instead of IPv4|6 for networking?
21–30 of 38 posts
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#22Routing packets based on MACs would be impossible. That's why. My laptop has the same MAC whether it is connected at home, at work, or in the airport. How would ISPs and the internet backbone routers know where to send the packets to reach me?
There's some interesting research in this area, but the current state of the art is pretty inefficient. http://www.cs.uiuc.edu/~caesar/papers/rofl.pdf http://conferences.sigcomm.org/co-next/2010/CoNEXT_papers/20...
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#23Typically, MAC is assigned by the hardware manufacturer (sometimes you can change/spoof it). IP is typically assigned either by the network administratior or DHCP. If all addresses were based on mac, you could easily intercept the messages from anyone. IP allows a layer of abstraction in which you can group multiple subnets into the same external IP or set up subnets within those subnets even. Another problem is that…
> If all addresses were based on mac, you could easily intercept the messages from anyone. So you encrypt stuff you don't want anyone else to read. Security isn't the concern of the networking layers; it's all done, to the extent it is done, at the application layer. That's the original design, anyway. Edited to add: Well, the original original designs were by people who weren't thinking of security at all. That's wh…
48 bits was intended to be globally unique
And it well could be, but guaranteeing uniqueness is rarely as easy of a problem as you might wish.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#24They already are. Part of the IPv6 address is derived from your MAC. Despite not owning the network for which they are being allocated, IPv4 is a "paying job" to some people. And sometimes an ego boost too, i.e., people who get their kicks from creating "IP address policy". Needless to say this easy "work." Hello ARIN. It's a lot like ICANN. On CircleID someone recently pointed out that IPv6 will make this sort of "j…
No. An IPv6 address can be partially derived from a MAC, but a lot of the time it won't be. For instance, none of the VMs we operate (which all have an IPv6 /64 assigned) have real network hardware, so it makes no sense to generate the IPv6 address from a MAC there. And you can still multihome a single IPv6 address across more than one physical interface, so again, that's not somewhere you'd want to put a MAC into an…
For instance, none of the VMs we operate (which all have an IPv6 /64 assigned) have real network hardware, so it makes no sense to generate the IPv6 address from a MAC there.
But each vNIC does have a subnet-unique MAC address, right? Why not use it?
And you can still multihome a single IPv6 address across more than one physical interface, so again, that's not somewhere you'd want to put a MAC into an IP address.
As long as you break the tie deterministically, I don't see the harm in picking one of the interface MACs.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#25Earlier quoted context omitted.
This is one of the reasons why IPX was a bad idea and never took off. Automagical discovery is always great until it doesn't work.
and never took off. IPX was everywhere NetWare was. NetWare got into everything, like dust, in the 80s and part of the 90s.
Being prevalent, which it no doubt was, and being pervasive are two different things.
IP has a way of worming itself into every little thing. IPX never really escaped from the desktop network environment.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#26Earlier quoted context omitted.
and never took off. IPX was everywhere NetWare was. NetWare got into everything, like dust, in the 80s and part of the 90s.
Being prevalent , which it no doubt was, and being pervasive are two different things. IP has a way of worming itself into every little thing. IPX never really escaped from the desktop network environment.
I did not know that pervasive was synonym for 'took off'.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#27Routing packets based on MACs would be impossible. That's why. My laptop has the same MAC whether it is connected at home, at work, or in the airport. How would ISPs and the internet backbone routers know where to send the packets to reach me?
Routing at layer 2 (via MAC) is already implemented in the data center. See TRILL or Cisco's FabricPath.
At Internet scale, LISP (http://www.lisp4.net/) takes on the problem of a 'static' host address being reachable at any location.
Both of these rely upon the idea of encapsulation (mac-in-mac or ip-in-ip) to separate the location and host identity.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#28None of the reasons given seem correct to me. Many of the reasons I see given are conventions arising from use and misuse.
The simple answer is this:
An IP address identifies a host, whilst a MAC address identifies an interface.
That is all.
Absolutely everything else, such as route aggregation, routing policy, and the behavioural differences between layers, stems from this primary distinction between logical and physical.
(Note: it remains a common - indeed, conventional - configuration & design error to bind an IP address to an interface. There is no such requirement and this complicates many networks. I was irritated to learn that IPv6 makes use of the MAC address in self-autoconfiguration)
(ObAuthority: I used to make ISP management systems for a living)
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#29None of the reasons given seem correct to me. Many of the reasons I see given are conventions arising from use and misuse. The simple answer is this: An IP address identifies a host, whilst a MAC address identifies an interface. That is all. Absolutely everything else, such as route aggregation, routing policy, and the behavioural differences between layers, stems from this primary distinction between logical and phy…
> An IP address identifies a host, whilst a MAC address identifies an interface.
... while a MAC can host multiple IP addresses (see vmware bridged network for guest OS), and the same interface can have multiple MAC addresses. And a devince can have multiple real/virtual interfaces.
Re: Why couldn't MAC addresses be used instead of IPv4|6 for networking?
#30We need a public service announcement to show the differences, something along the lines of "I'm a MAC, I'm an IP"