[c-nsp] L4 ports in 'mls ip cef load-sharing full'

[Everton da Silva Marques]

The task at hand is to figure out whether "mls ip cef
load-sharing full" would make a good use of L4 ports. "Good
use" would produce, from randomly chosen L4 ports, a
reasonably uniform distribution of output interfaces.

Platform is: IOS 12.2(18)SXE4 under 7609, experimenting with
a pair of parallel p2p output links.

Cisco's command reference about "mls ip cef load-sharing
full" states:

  full (Optional) Sets the CEF load balancing to include
  source and destination Layer 4 ports and source and
  destination IP addresses (Layer 3).

However, experiments are leading me to believe that changes
in L4 ports scarcely affect the selection of the output
interface. That is, for a fixed pair of source-destination
addresses, most changes of (either source or destination) L4
ports keep yielding the same output interface.

Can anyone confirm this, or shed some light on why changes
in L4 ports seem to produce such uneven distribution of
output links?

Thanks,
Everton