Rolf Fokkens
2010-Dec-19 22:16 UTC
[Bridge] Why should static MAC address match one of the port MAC addresses.
Hi all,
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).
So, Michiel's claim still seems to be true: the bridge mac address
should apparently be one of the bridge interfaces.
I don't see the logic, this seems like a bug to me.
Cheers,
Rolf
------------------------------------------------------------------------
* /To/: Michel Lammertink <mlammertink at xxxxxxxxx
<mailto:mlammertink at DOMAIN.HIDDEN>>
* /Subject/: Re: Why should static MAC address match one of the port
MAC addresses.
* /From/: Stephen Hemminger <shemminger at xxxxxxxxxxxxxxxxxxxx
<mailto:shemminger at DOMAIN.HIDDEN>>
* /Date/: Tue, 12 Oct 2010 09:44:08 -0700
* /Cc/: bridge at xxxxxxxxxxxxxxxxxxxxxxxxxx <mailto:bridge at
DOMAIN.HIDDEN>
* /In-reply-to/: <4CB46549.2070901 at xxxxxxxxx
<mailto:4CB46549.2070901 at DOMAIN.HIDDEN>>
* /Organization/: Linux Foundation
* /References/: <4CB46549.2070901 at xxxxxxxxx
<mailto:4CB46549.2070901 at DOMAIN.HIDDEN>>
------------------------------------------------------------------------
On Tue, 12 Oct 2010 15:40:25 +0200 Michel Lammertink<mlammertink at
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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Rolf Fokkens
2010-Dec-19 22:19 UTC
[Bridge] Why should static MAC address match one of the port MAC addresses.
Forgot some specifics: kernel is Fedora kernel-2.6.35.9-64.fc14.x86_64. On 12/19/2010 11:16 PM, Rolf Fokkens wrote:> Hi all, > > 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). > > So, Michiel's claim still seems to be true: the bridge mac address > should apparently be one of the bridge interfaces. > > I don't see the logic, this seems like a bug to me. > > Cheers, > > Rolf > > ------------------------------------------------------------------------ > > * /To/: Michel Lammertink <mlammertink at xxxxxxxxx > <mailto:mlammertink at DOMAIN.HIDDEN>> > * /Subject/: Re: Why should static MAC address match one of the > port MAC addresses. > * /From/: Stephen Hemminger <shemminger at xxxxxxxxxxxxxxxxxxxx > <mailto:shemminger at DOMAIN.HIDDEN>> > * /Date/: Tue, 12 Oct 2010 09:44:08 -0700 > * /Cc/: bridge at xxxxxxxxxxxxxxxxxxxxxxxxxx > <mailto:bridge at DOMAIN.HIDDEN> > * /In-reply-to/: <4CB46549.2070901 at xxxxxxxxx > <mailto:4CB46549.2070901 at DOMAIN.HIDDEN>> > * /Organization/: Linux Foundation > * /References/: <4CB46549.2070901 at xxxxxxxxx > <mailto:4CB46549.2070901 at DOMAIN.HIDDEN>> > > ------------------------------------------------------------------------ > On Tue, 12 Oct 2010 15:40:25 +0200 Michel Lammertink<mlammertink at 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./-------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.linux-foundation.org/pipermail/bridge/attachments/20101219/6ade53e1/attachment-0001.htm