[ale] failover planning

[Stephan Uphoff]

On Mon, 2004-11-29 at 21:01, Christopher Fowler wrote:
> On Mon, 2004-11-29 at 20:56, Stephan Uphoff wrote:
> > On Mon, 2004-11-29 at 20:34, Christopher Fowler wrote:
> > > I've tried this before with simple configuration of two nics simply
> > > using ifconfig.  But I was never convinced that packets destined for 2.5
> > > was not scooped up by the first nic on 2.4
> > 
> > When I transitioned from cable to dsl I had such a setup.
> > The problem was that BOTH nics would reply to broadcasted ARP request
> > for either of the IPs with their own Ethernet address.
> > This caused packets to arrive at the wrong interface where they were
> > blocked by a firewall. (This was an old hacked up 2.2.16? kernel)
> > 
> 
> If I unplug 2.5 then all pings to 2.5 should fail.  That is at least
> what I want to happen.

This won't work with the 2.2.16? kernel - I can't say anything about
newer kernels.

This being said - even if newer linux versions have the same problem you
could now theoretically use the firewall at the link layer to filter out
ARP packets received/transmitted from/to the wrong interface.

Try it - run a tcpdump - see if both interface answer ARP requests.

	Stephan