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From: Chandrashekarappa <nandinic1@gmail.com>
To: bridge@lists.linux-foundation.org
Subject: [Bridge] Fwd: What is the lowest valid MAC address that can be assigned to a NIC/bridge?
Date: Mon, 8 Mar 2010 16:32:11 -0500	[thread overview]
Message-ID: <8f2d78ba1003081332v539dbebeo7b6ef46f2c48c620@mail.gmail.com> (raw)
In-Reply-To: <1883282645.390611268083800046.JavaMail.root@zmail04.collab.prod.int.phx2.redhat.com>

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My setup:
I have a machine running RHEL 5.4(kernel - 2.6.18-164.el5)with two NICs.I've
created a bonded interface bond0 with the 2 NICs(eth0 and eth1),added bond0
to the bridge br0.

When I create the bonded interface bond0,bond0 gets the MAC address of the
first slave device(eth0 in my case)
After I create br0 and add bond0 to br0,br0 gets the MAC address of bond0.

Issue:
-I then add a third ethernet interface eth2 to br0
-br0 now acquires the MAC address of eth2
-I'd like it if the MAC address of br0 *didn't change*.

My analysis:
-A bridge acquires the lowest MAC address of all the ports connected to
it.So,I do believe the bridge acquiring a new MAC address every time an
ethernet interface is added or removed from a bridge is expected.
-I also found this patch in the 2.6.27 upstream kernel :
92c0574f11598c8036f81e27d2e8bdd6eed7d76d
bridge: make bridge address settings sticky

Normally, the bridge just chooses the smallest mac address as the
bridge id and mac address of bridge device. But if the administrator
has explictly set the interface address then don't change it.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Possible workaround:
I think I should be able to work around this issue by assigning the lowest
valid MAC address to one of my ethernet interfaces before adding it to
br0.I'd like to know what is the lowest valid MAC address that can be
assigned to a NIC.
http://standards.ieee.org/regauth/groupmac/tutorial.html

I'd appreciate any pointers.

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       reply	other threads:[~2010-03-08 21:32 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1826249814.390491268083744068.JavaMail.root@zmail04.collab.prod.int.phx2.redhat.com>
     [not found] ` <1883282645.390611268083800046.JavaMail.root@zmail04.collab.prod.int.phx2.redhat.com>
2010-03-08 21:32   ` Chandrashekarappa [this message]
2010-03-08 22:03     ` [Bridge] Fwd: What is the lowest valid MAC address that can be assigned to a NIC/bridge? richardvoigt
2010-03-09  7:22       ` Stephen Hemminger

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