[c-nsp] Uneven LACP load-balancing

[Brandon Ewing]

On Fri, Nov 12, 2010 at 11:40:37AM -0600, Brandon Ewing wrote:
> 
> Unfotunately, I don't know if the layer-2 hashing method on src-dst-ip is
> independent of whichever CEF algorithm I choose, or if both load balancing
> levels always use the same algorithm.
> 

As a follow-up, I tried switching between the various different CEF hashing
algorithms with "ip cef load-balance algorithm", but none of the changes
altered the polarization I was seeing.  

Since I have no downstream etherchannels, only upstream, I finally resolved
the issue by changing the port-channel balance method to dst-ip only.  Once
I did that, traffic was evenly distributed.  Since I only have port-channels
going on one direction, I don't need to worry about polarization downstream
to the servers.

I would still classify this as a bug, or request additional features to
allow one to alter the layer 3 hash ID and layer 2 hash ID seperately to
avoid issues such as this where src-dst-ip hashing is required at layer 2.
My testing appears to indicate that since both the layer 3 hash and layer 2
hash are the same, links that choose one L3 interface will always choose the
same L2 interface inside the individual bundle.  Being able to seed them
independently should resolve this issue.

-- 
Brandon Ewing                                        (nicotine at warningg.com)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <https://puck.nether.net/pipermail/cisco-nsp/attachments/20101112/aee04d63/attachment-0001.bin>