Re: how to change mac address back after decnet changed it?
On Mon, Sep 05, 2011 at 02:10:11PM +0200, Steven wrote:
> Dear Debian users,
> Some time ago, an update on my wheezy system brought in dnet-common and
> some related packages. I noticed that decnet changes the hardware
> address of my interfaces, but didn't pay much attention to it, figuring
> they would at least be unique, so I could fix up dhcp later. Having a
> different IP for some time isn't all that bad in my setup.
> However now I noticed that these hardware addresses are certainly NOT
> unique. I have a machine with 2 NICs and both have aa:00:04:00:0a:04 as
> hardware address (second one isn't plugged in physically), so is the
> eth0 interface on my laptop. This obviously can't be right.
> I already uninstalled the dnet-common package from 1 machine, but to no
> effect after rebooting. It's neither an option when reconfiguring the
> dnet-common package.
According to wikipedia, this is a feature, not a bug:
| The Ethernet implementation was unusual in that the software changed
| the physical address of the Ethernet interface on the network to
| AA-00-04-00-xx-yy where xx-yy reflected the DECnet network address of
| the host. This allowed ARP-less LAN operation because the LAN address
| could be deduced from the DECnet address. This precluded connecting two
| NICs from the same DECnet node onto the same LAN segment, however.
So your DECnet address would be 0x0A04.
> So how do I get rid of that aa:00:04:00:0a:04 address? And getting the
> old ones back, note that I do not remember the old ones, nor do I have
> them all written out somewhere.
You should be able to set the address with:
$ ifconfig ethN hw ether aa:bb:cc:dd:ee:ff
The value of the address doesn't really matter so long as it's unique on
your ethernet segment (i.e. your network). Then again, if you're doing
some sort of bonding or balancing, it doesn't even have to be unique.