Author: Jacqui Caren Date: To: Hampshire LUG Discussion List Subject: Re: [Hampshire] One box, 2 NICs - but with the same MAC address
Graham Bleach wrote: > A common scenario is two use two separate physical switches, trunked
> together to provide a single broadcast domain. Each host has two
> physical interfaces, one connected to each switch. The OS then uses
> some form of interface failover mechanism (e.g. bonding on Linux, IP
> multipathing on Solaris) to detect when an interface has failed and
> deactivate it, using the alternate network path. This failover process
> is almost transparent to most applications. If we didn't have
> monitoring we wouldn't even have noticed the switch failures we've had
> in the last couple of years.
The added advantage of bonded interfaces is that it is not just failover
but both NICs are in operation, so you have (almost) double bandwidth.
Note: For failover having two identical NICs is just plain insane,
as if they are from the same batch and have the same fault (seen it
happen too many times with bulk box purchases) then they could both die
in rapid succession.
Finally as pointed out above you need to manage failover which means
detection and recovery. Replacing a dead NIC is not like a hot swap
drive - you have to take the box down which I would assume is a no-no.
Therefore you need three different NICs, one of which is unconfigured
- this takes over from the dead NIC when (not if, when) it dies.
