[nsp] Etherchannel

[Dmitri Kalintsev]

On Tue, Feb 18, 2003 at 09:17:28PM +0100, Gert Doering wrote:
> On Tue, Feb 18, 2003 at 03:03:51PM -0500, Jason Greenberg wrote:
> > We used Etherchannel in an backbone environment between a 7513 and a
> > 2900xl, and we only found that it was buggy, unreliable, and was a poor
> > load-balancer.
> 
> The way it load-balances is *not* "per-packet" (due to ethernet packet 
> ordering constraints).  It's mostly by source/destination MAC address,
> so if you have a router on one end, load-balancing is likely to be poor.

I believe it will do per-packet from the router towards the switch (which
will be OK), but per src/dest MAC from the switch towards the router (which
will suck, especially if most of the traffic towards our router is sourced
by a small number of MACs - think "other router(s)").

> > Has anyone on the list used Etherchannel in an ISP backbone before?  I
> > find that I much prefer layer 3 balancing for stability and
> > manageability.
> We use it between a couple of Catalysts 5500/5000s and one 2900XL that do 
> not have GigE yet.  Some links are 2x 100, some are 4x 100, and all of
> them work as expected, due to the wide variation of traffic peers on
> that networks.

Well, *between switches* it's no problem. Between a *router* AND a *switch*
it is very likely to be a problem (why - I've described above).

SY,
-- 
D.K.