On Wed, Mar 03, 1999 at 06:03:01PM -0800, Sam Cramer wrote:
Jeff writes:
I created me a vif interface made up of four 100Mb Ethernet interfaces.
I see, that only the first two interfaces really do anything, the second two show no errors, but dont DO anything.
It's my understanding that etherchannel switches use a proprietary protocol to distribute load over the links. This protocol often involves a hash of the source and destination addresses. It may be that you have a pattern of access from specific clients that doesn't hash well, and so doesn't distribute the load over all the links.
Remember that etherchannel is "EtherChannel(tm)" when used on a Cisco switch. :) I don't believe there is an IEEE standard yet, but Sun and Cisco at least use the same routines:
You need an EBC (Ethernet Bundling Controller) on the blade of the CAT, since it's what ultimately decides which link the packet will go out. The EBC calculation that determines which link is used is very simple, as you mentioned. The connection across the etherchannel is determined by the source address and destination address pairs. The EBC performs an X-OR operation on the last two bits of the source MAC address and destination MAC address. This operation yields one of four results: (0 0), (0 1), (1 0), or (1 1). Each of these values points to a link in the Fast EtherChannel bundle.
So without knowing exactly how the host/netapp decide which MAC address is used on outgoing packets, it's hard to say how the "balancing" is done.. The main thing to remember is that the balancing is not packet-per-packet as that would introduce the potential for out-of-order packets (then the application would have to request retransmission, which while perfectly normal, is going to kill you performance wise). The SUN quad card comes with trunking software, I don't know how it works.
At any rate, the Cisco site has some pretty decent docs on etherchannel.
Personally, after evaluating EC on an F740, I've pretty much come to the conclusion that for end-to-end throughput, Gigabit is a much better solution. For balancing a bunch of clients to a "link-redundant" IP though, the etherchannel is neat stuff.
cya, -Mark