Swapping MAC addresses?

John LLOYD jal at mdacorporation.com
Thu Sep 3 11:53:06 CDT 2009


> Date: Thu, 3 Sep 2009 09:14:17 -0700
> From: John Oliver <joliver at john-oliver.net>
> Subject: Re: Swapping MAC addresses?
> To: linux-poweredge at lists.us.dell.com
> Message-ID: <20090903161417.GA12153 at ns.sdsitehosting.net>
> Content-Type: text/plain; charset=us-ascii
> 
> On Wed, Sep 02, 2009 at 05:18:48PM -0700, Chase Bolt wrote:
> > I can't imagine he is rebooting once a week, though if he 
> was I would 
> > lean more towards Bryan on this.
> 
> I am not :-)  Current uptime is 35 days.  And that reboot was 
> after this
> was reported...
> 
> BTW, the config files *do* contain HWADDR lines.
> 
> > Only time I have seen macs flipping like this so often is 
> when your have 
> > bonded your nics. Are you doing a load balance or 
> active/passive setup 
> > on your nics?
> 
> Nope.
> 
> [joliver at mda-services ~]$ sudo cat
> /etc/sysconfig/network-scripts/ifcfg-eth0
> # Broadcom Corporation NetXtreme II BCM5708 Gigabit Ethernet
> DEVICE=eth0
> HWADDR=00:19:b9:ca:5b:44
> IPADDR=XXXXXXXXX.129
...snip...
> [joliver at mda-services ~]$ sudo cat
> /etc/sysconfig/network-scripts/ifcfg-eth1
> # Broadcom Corporation NetXtreme II BCM5708 Gigabit Ethernet
> DEVICE=eth1
> HWADDR=00:19:B9:CA:5B:46
> IPADDR=XXXXXXXXX.47

There's your problem -- they are on the same subnet, no?  (your '129 IP
and '47 IP have the same left-hand side).  You have two NICs on the same
subnet.

You need to bond them, or disconnect one, or adjust some ARP tuning,
e.g. arp_filter=1 to force one or the other (only) to respond to arp
requests.

(Think of it from the linux kernel point of view.  It has a packet in
hand, ready to go out to your subnet XXXXXXXX.  Which interface should
it use?  It has a choice of two, so, clearly, it is changing it's mind
from week to week....)


--John



More information about the Linux-PowerEdge mailing list