Multiple NICS - Real Servers

Jake Garver garver at
Thu Aug 9 04:42:02 BST 2001

I'm not a CCNA, but I play one at work.

> It would be nice if it could work across multiple switches, so if a
> single switch failed, you would not lose connectivity (I think the
> adaptive failover can do this, but that does not improve bandwidth).

No it wouldn't be nice because it would put a tremendous burdon on the
link connecting the switches.  If you are lucky, this link is 1Gb/sec, much
slower than back planes which or 10Gb/sec and up.  In general, you don't
want to "load balance" your switches.  Keep as much as you can on the same
back plane.

> Even so, in a Cisco Catalyst chassis with multiple blades and redundant
> supervisor cards (and power supplies, obviously), this might be a decent
> HA/performance solution.  I'll have to look at the back of those big
> Ciscos and see if they have multiple power cables.  I find it amusing
> that a Sun 4500 can have four power supplies (and a 450 can have two),
> but since they have a single power cord, one clumsy person can take
> the system down quite easily.  In my experience, that kind of thing
> happens far more often than equipment failure.  HA is all about
> attention to details.

Any Cisco chassis' (4000s, 5000s, and 6000s) have multiple power supplies,
with its own power chord.

> So, are there any Cisco Fast EtherChannel experts out there?  Can
> FEC run across multiple switches, or at least across multiple Catalyst
> blades?  I guess I can go look it up, but if somebody already knows,
> I don't mind saving myself the trouble.

Fast EtherChannel cannot run across multiple switches.  A colleague spent
weeks of our time proving that.  In short, each switch will see a distinct
for a total of two, but your server will think it has one big one.  The
switches will not talk to each other to bond the two links and you don't
them to for the reason I stated above.  Over multiple blades, that depends
on your
switch.  Do a "show port capabilities" to find out; it will list the ports
that can be grouped into an FEC group.

Jake Garver

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