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RE: Fast Switching [7:87402] posted 04/16/2004
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Gould, Aaron M (NRSW N61CR1W) wrote:
> 
> thanks for being so gentle priscilla.  ha
> 
> thanks for being my sounding board.....i sort of thought this
> through after
> i sent the email to the group.  it didn't seem that switching
> is even a
> question when it doesn't have to switch (in one int and out
> another int)
> just as you stated priscilla....but you did bring up a good
> question....whether or not it uses some fast-switching cache or
> cef
> switching cache for L2 encap info when it sources packets. ?
> 
> is this the book you are referring to?  
> 
> Inside Cisco IOS Software Architecture (CCIE Professional
> Development) -
> 1578701813

Yes, I think that's it. It's supposed to be really good. I don't have it
though. Do you or anyone else have it and could check out this question? It
seems like the sort of thing that would be in there.

Priscilla


> 
> thanks again
> 
> aaron
> 
> 
> Aaron Gould (CACI)
> Network Engineer, PACSW/CNRSW/RITSC
> 619-545-2569
> 619-981-4900 cell
> <> 
> 
> -----Original Message-----
> From: Priscilla Oppenheimer [mailto:nobody@xxxxxxxxxxxxxx]
> Sent: Friday, April 16, 2004 2:12 PM
> To: cisco@xxxxxxxxxxxxxx
> Subject: RE: Fast Switching [7:87402]
> 
> 
> Gould, Aaron M (NRSW N61CR1W) wrote:
> > 
> > does ip traffic sourced or destined for router "A" ever get
> > fast switched on
> > router "A"?  or is it always going to be processed switched on
> > router "A"
> > when it is sourced and/or destined for router "A"?
> 
> There is no switching in those examples. Think about what
> switching means,
> i.e. forwarding, relaying, moving something to a different
> position. In
> electronics, switching permits or interrupts the flow of
> current through an
> electrical circuit. In the transportation industry, switching
> turns a
> locomotive from one track to another. In the networking field,
> switching
> takes bits, frames, packets in one interface and sends them out
> another.
> 
> So, what are you really asking? 
> 
> When a router receives a packet destined for itself, it
> recognizes right
> away that the destination is itself and doesn't have to check
> any switching
> cache.
> 
> When a router sends a packet on its own (rather than switches a
> packet), the
> question becomes more relevant. I would imagine it can look up
> the
> destination address in the fast-switching cache or whatever
> other advanced
> cache it uses. That would make sense. That Cisco IOS
> architecture book that
> people mention sometimes might answer this in more definite
> terms.
> 
> Priscilla
> 
> > 
> > thanks
> > 
> > aaron
> > 
> > 
> > 
> > Aaron Gould (CACI)
> > Network Engineer, PACSW/CNRSW/RITSC
> > 619-545-2569
> > 619-981-4900 cell
> > <> 
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