[c-nsp] etherchannel between different switches

[Aaron Daubman]

Hi Tassos,

> I would like to ask if there are any switches (cisco or non-cisco) that support etherchannel
> functionality between different physical switches.
> I know that the 3750s can do this through their stack implementation, but i'm looking for bigger
> ones, like 6500s.

Nortel is the only vendor I know of that allows this - using SMLT:
http://en.wikipedia.org/wiki/Split_Multi-link_Trunking_(SMLT)

I'm not a huge fan (warning: possibly personally skewed bias against
Nortel) and have heard mutterings that there are "interesting/hidden
downsides" to this.  (I have no concrete details, however)

Having operationally implemented SMLT, however, when it works it
really does seem to 'magically' distribute traffic between access
switches and multiple cores... you do, however, lose determination
which makes troubleshooting fun... there were also certain protocol
limitations imposed when enabling SMLT on a switch, however this may
have changed...  (I was only involved with the initial roll out, and
so cannot speak to long-term benefits/issues either)

YMMV - depending on your network design you may also be able to
benefit from GLBP (or GLBP + EtherChannel):
http://en.wikipedia.org/wiki/GLBP

All-in-all, although not as auto-magical, a "properly" implemented
network using 802.1w/PVST+ will, in essence, provide the same
functionality as well as determinism when hunting down problems...
(this seemed to be Cisco's response to "why no SMLT?" early on at
least - anybody have better/more current details?  How about concrete
info on SMLT performance/issues/benefits?)

Just my $0.02 - please add NaCl,
     ~Aaron