Swapping MAC addresses?

[Chase Bolt]

Yup this is the exact problem you are having. This is what I keep in my 
sysctl.conf file:

[root at xxxx ~]# cat /etc/sysctl.conf

*Snipped*

# ARP Fix
net.ipv4.conf.default.arp_filter=1
net.ipv4.conf.all.arp_filter=1
net.ipv4.conf.all.rp_filter=0
net.ipv4.conf.default.rp_filter=0
[root at xxxx ~]#

Make sure to run sysctl -p or restart your network service to make these 
changes live.


John LLOYD wrote:
>> 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
>
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