Re: Asymmetric traffic/topology

[Roland Dobbins <rdobbins () cisco com>]

On Nov 13, 2007, at 11:28 AM, Jeremy Bennett wrote:

> What I meant was systems that are attempting to extract flow data  
> by watching the traffic itself.

These must be placed at appropriate points in the topology, yes, if  
the infrastructure itself doesn't support NetFlow export.  nfdump  
would be an example of the type of system you're describing; for  
example, Adam's Lancope collectors can also generate flows from RSPAN  
or copy/capture VACL destination ports, if necessary.

The disadvantage of this mode of operation is that a) it doesn't  
scale well, as you indicate, and b) one loses the input and output  
ifindex information, and thus the traceback functionality is impeded.

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