[c-nsp] Cisco Fast EtherChannel vs. IEEE 802.3ad ?

[Brett Frankenberger]

On Wed, Aug 02, 2006 at 12:09:19PM -0400, Ed Ravin wrote:
> We're using a Cisco Fast EtherChannel trunk between our 7513 and
> an elderly HP ProCurve.  The ProCurve has a config setting for trunks
> where it explicitly says "FEC mode". The Cisco is set up with a
> "Port-Channel" interface and all is well.
> 
> But I'm shopping for a new switch to replace the ProCurve, and the newer
> ProCurve switches seem to all support IEEE 802.3ad / LACP, with no mention
> of EtherChannel.  Googling around a bit, it seems that Cisco Fast EtherChannel
> might be a subset of IEEE 802.3ad or vice versa, but it's not clear, since
> I also see mention that Cisco Fast EtherChannel is proprietary and had to
> be specially licensed to HP.

EtherChannel isn't really a protocol -- it just conceptually means the
switch/router treats the ports as a single entity, splitting outbound
traffic and accepting traffic on either port.  There are no control
packets indicating that that's what's happening.  It's a subset of
802.3ad in the sense that an Etherchannel works (by configuration)
similarly to an 802.3ad negotiated bundle.  The difference is that
EtherChannel byitself doesn't negotiate anything; if you tell it to put
two ports in a bundke, that's what it does.

IEEE 802.3ad is a standards based protocol for negotiating the
aggregation, Cisco also has it's own proprietary version (PAgP).  But
cisco stuff can also be configured just to combine the ports without
any protocol for negotiating it.  (This is how I set everything up,
even my Cisco<->Cisco aggregate links).  I'm not aware that Cisco
supported LACP or PAgP on any routers, but I could easily be wrong --
as I said, I don't use any of those protocols anyway.

If your new switch supports a "just stop trying to negotiate anything,
and aggregate these ports because I told you to" mode, it should work
fine with the 7513.  If it can't be configured to aggregate ports
except after a successful LACP negotiation with the other end (I'd be
surprised if that were the case), then you've probably got a
compatibility problem with the 7513.  

     -- Brett