[c-nsp] etherchannel load-balancing and unpredictability

[Steven Pfister]

I have a question regarding etherchannel load balancing. I've got a
4507R switch connected to a 3560 switch by means of two content filters
which are acting as transparent bridges. The two ports on each side that
the content filters are connected to are set up as access ports and are
in an etherchannel. The load balancing method on each switch is set to
src-dst-ip. I was under the impression that each pair of source and
destination ip address would select exactly one content filter no matter
which direction. 
 
I've been told that this can be 'unpredictable' and may cause
assymetric flows. The algorithm seems fairly straightforward to me. I
don't see where the unpredictability can come in. Can someone explain to
me what I'm missing?
 
 
Steve Pfister
Network Engineer
Office of Information Technology
Dayton Public Schools
115 S Ludlow St
Dayton, OH 45402-1812
Phone: 937-542-3149
Cell: 937-673-6779
spfister at dps.k12.oh.us ( mailto:spfister at dps.k12.oh.us )