[CentOS] oops, or how to bring a datacenter router down with one setting

Fri Feb 10 13:48:46 UTC 2012
Dennis Jacobfeuerborn <dennisml at conversis.de>

On 02/10/2012 11:18 AM, Tony Mountifield wrote:
> In article<4F345CD3.4060604 at bobhoffman.com>,
> Bob Hoffman<bob at bobhoffman.com>  wrote:
>> so I gave up on bonding.
>> I found about 300 posts showing eth0 and eth1 both pointing to br0 (bridge)
>> as interfaces.
>> I followed them correctly, or so I thought.
>> I pointed both ethx to the bridge, restarted network and bam...!!!
>> entire ip block went out.
>> [...]
>> Feb  9 04:22:41 main kernel: __ratelimit: 100807 callbacks suppressed
>> Feb  9 04:22:41 main kernel: eth1: received packet with own address as
>> source address
> I think to do this you also need to be connected to a managed switch
> which supports interface bonding. You would have to tell it that the two
> switch ports are bonded to the same machine. That should prevent it from
> forwarding packets received on one of the ports out via the other port.
> The key phrase to look for appears to be "IEEE 802.3ad Dynamic Link
> Aggregation".

Yes, linux support LACP but it's just one of the possible bonding modes. 
The other ones can work without special switch support i.e. "Active-backup" 
only works with one port and the other only comes into play when the first 
one fails.