[nsp] ip cef

[Sam Stickland]

Out of interest, which versions of IOS started supporting CEF in the process
path?

----- Original Message -----
From: "Oliver Boehmer (oboehmer)" <oboehmer at cisco.com>
To: "James Galliford" <JamesG at corp.ptd.net>; "Hugo" <netw2004 at hotmail.com>
Cc: <cisco-nsp at puck.nether.net>
Sent: Monday, December 01, 2003 8:51 PM
Subject: RE: [nsp] ip cef


>
>
> > I believe that if the router does not have the route in its CEF table
> > that it process switches the first stream and therefore you'll see the
> > entry in the ip cache.  After the router knows the path and determines
> > the optimum switching method, it will then create an entry in the CEF
> > table for the path.  The path will then be invalidated from the route
> > cache.
> >
> > This is to the best of my understanding of course.
>
> But this is wrong ;-), you are basically describing fast switching. CEF
> is not a demand-based cache, it is populated from the routing table.
> When we try to CEF-switch a packet and there is no FIB entry for the
> destination, the packet is dropped.
>
> Hugo: you're possibly seeing entries in the fast cache for packets
> processed by the CPU, including packets generated by the router itself.
> Newer IOS releases also use CEF in the process path..
>
> oli
>
> > -----Original Message-----
> > From: Hugo [mailto:netw2004 at hotmail.com]
> > Sent: Monday, December 01, 2003 3:01 PM
> > To: James Galliford
> > Cc: cisco-nsp at puck.nether.net
> > Subject: Re: [nsp] ip cef
> >
> >
> > Hi James!!!
> >
> >           You are right. Now I see less entries in the table, but I
> > thought that all the packets would be cef switched. Why not? Thanks!!!
> >
> >
> > ----- Original Message -----
> > From: "James Galliford" <JamesG at corp.ptd.net>
> > To: "Hugo" <netw2004 at hotmail.com>; <cisco-nsp at puck.nether.net>
> > Sent: Monday, December 01, 2003 8:24 PM
> > Subject: RE: [nsp] ip cef
> >
> >
> > Hugo,
> >
> > Whenever any packet is process switched you will see an addition to
> > the # of adds in the ip cache output.
> >
> > You are probably seeing a much lower # of entries in the route cache
> > since turning on cef though correct?  If not, maybe CEF is not running
> > on all interfaces?
> >
> > Thanks.
> >
> > -----Original Message-----
> > From: Hugo [mailto:netw2004 at hotmail.com]
> > Sent: Monday, December 01, 2003 12:43 PM
> > To: cisco-nsp at puck.nether.net
> > Subject: [nsp] ip cef
> >
> >
> > Hi!!!
> >
> >
> >              Just an easy question. I have just enabled Ip cef on my
> > router, but I still see new entries in the cache table when I execute
> > the "show ip cache" command. Could someone tell me if this is the
> > right way of cef working? Thanks!!!
> >
> > Regards
> >
> > H
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