[opendtv] IP vs. MAC addresses (was: Twang's Tuesday Tribune)
- From: Segal Gary-r36550 <Gary.Segal@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 7 May 2004 13:48:27 -0700
> [mailto:opendtv-bounce@xxxxxxxxxxxxx]On Behalf Of Manfredi, Albert E
> Sent: Thursday, May 06, 2004 10:04 AM
> To: opendtv@xxxxxxxxxxxxx
>
> Actually, IPv6 uses 128 bit address fields. Wider than even the
> MAC address is. And one option if you want to auto-configure
> IPv6 addresses is to embed the MAC address of the device in the
> IPv6 address. You add a prefix to the MAC address, in essence.
> If you assume MAC addresses to be mostly unique, and you also
> implement a duplicate address detection algorithm, you will
> have a nifty way to assign IP addresses automatically, without
> DHCP.
You are right, IPV6 isn't 48 bits; it's 128 bits. I actually caught that and
meant to send out a correction, however I got messed up by a recent change to
my email address which caused me to have to re-subscribe to the list. I wasn't
able to send out my correction before work got in the way... :-)
Anyway, there still seems to be some confusion about the difference between a
logical address and a physical address. MAC addresses are physical addresses
that are supposed to be unique to each network node, while IP addresses are
logical and are assigned to physical devices on an as needed basis. IP
addresses are also "locality" based, in that they are tied to the network that
a device connects to. Move the device from one network to another, and the IP
address changes.
If some manufacturers are actually assigning random MAC addresses, that seems
like a bad thing to me. But in this age of cost cutting, it doesn't surprise
me.
-Gary Segal
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