Hi All,
Despite of what Stephen explains, I'm having the problem Michiel
describes as well. I have a bridge br2 containing 1 (but potentially
more) tap interface for kvm. Windows 7 VM doesn't like the bridge mac
address to change, so I try to make it fixed.
ifconfig br2 hw ether 02:00:00:00:01:02
Interface br2 becomes instantly unreachable from the VM (via the tap
interface). No arp response or anything else.
So, Michiel's claim seems to be true: the bridge mac address should
apparently be one of the bridge interfaces. But I don't see the logic,
this seems like a bug to me.
kernel is Fedora kernel-2.6.35.9-64.fc14.x86_64.
Cheers,
Rolf
------------------------------------------------------------------------
* /To/: Michel Lammertink <mlammert...@xxxxxxxxx
<mailto:[email protected]>>
* /Subject/: Re: Why should static MAC address match one of the
port MAC addresses.
* /From/: Stephen Hemminger <shemmin...@xxxxxxxxxxxxxxxxxxxx
<mailto:[email protected]>>
* /Date/: Tue, 12 Oct 2010 09:44:08 -0700
* /Cc/: bri...@xxxxxxxxxxxxxxxxxxxxxxxxxx
<mailto:[email protected]>
* /In-reply-to/: <4cb46549.2070...@xxxxxxxxx
<mailto:[email protected]>>
* /Organization/: Linux Foundation
* /References/: <4cb46549.2070...@xxxxxxxxx
<mailto:[email protected]>>
------------------------------------------------------------------------
On Tue, 12 Oct 2010 15:40:25 +0200 Michel Lammertink<mlammert...@xxxxxxxxx>
wrote:
>/ Hi all,/
>/ /
>/ I've read many messages on this mailing list with the question about/
>/ setting a static MAC address on the bridge interface, but two questions/
>/ remain:/
>/ /
>/ 1. Why should the MAC address of the bridge match the address of one of/
>/ its interfaces? Setting the MAC address to a different value does not/
>/ generate an error, but the bridge is not working properly (Local data/
>/ does not arrive)./
No longer a requirement. It was just a good way to ensure a good
address that was unique, and not being used by other systems.
>/ 2. Why does the bridge by default choose the "lowest" MAC address,/
>/ instead of the MAC address of the first port added, as is proposed by/
>/ the standard [1]?/
It was a convenience in original design to choose a consistent value.
Since ports can be added in any order, using the lowest seemed like
a good idea for the original author. This has been maintained for
backwards compatibility.
>/ [1] IEEE802.1D, Par. 7.12.5./
>/ Quote: "The Bridge Address may be the individual MAC Address of a/
>/ Bridge Port, in which case, use of the address of the lowest numbered/
>/ Bridge Port (Port 1) is recommended."/
>/ /
>/ Thanks in advance,/
>/ /
>/ Michel./
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