Re: CPPr

Thanks guys! best Xmas present yet!

On Sun, Jan 3, 2010 at 6:54 AM, Tyson Scott <tscott_at_ipexpert.com> wrote:

> Hopalong/Miroslav,
>
> The third is the CEF exception not the CEF interface but you did a good job
> working thru the stuff Miroslav. CEF traffic typically doesn't leave the
> data plane; hardware/specialized software when traversing the router. The
> FIB allows the traffic to remain in the data plane without further
> processing by the router. Thus this traffic is not process switched.
>
> So just a comment on this CEF Exception interface for clarification. This
> would be traffic that typically is only meant to traverse the data plane of
> the router but is punted to the route processor for further processing
> either due to something like IP options in the packet that the router needs
> to check or an ACL or other feature configured on the router that causes
> further processing of CEF based traffic. Non IP traffic would not be
> forwarded by the router unless the router is configured to do so, for IPX
> or
> other non IP traffic. But this wouldn't be a good classification of what
> is
> considered to be the CEF exception traffic. I.E. ARP and CDP traffic
> wouldn't be CEF exception traffic as this is traffic that would be expected
> to be processed by the router as the traffic is not intended to be
> forwarded
> by the router to another subnet. ARP is part of the building block of the
> FIB and the CEF Table is not built without it; meaning it is a precursor to
> the CEF process.
>
> Regards,
>
> Tyson Scott - CCIE #13513 R&S, Security, and SP
> Technical Instructor - IPexpert, Inc.
> Mailto: tscott_at_ipexpert.com
> Telephone: +1.810.326.1444, ext. 208
>
>
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Miroslav Kosut
> Sent: Saturday, January 02, 2010 6:29 PM
> To: hopalong
> Cc: Cisco certification
> Subject: Re: CPPr
>
> Hello,
>
> it depends on the destination of this traffic:
>
> 1. If the traffic is destined for the web server running on the router
> (i.e.
> web gui), then the policy must be configured on the "host" subinterface.
> 2. If the traffic is supposed to be enter and leave the router, then the
> policy must be configured on the "top-level (aggregate)" interface.
>
> Basically, all three subinterfaces are used for packets which are handled
> specially (otherwise a policy should be configured on "top-level aggregate
> interface"):
>
> a) "host" subinterface - traffic destined to one of the router interfaces
> (examples: telnet, ssh, http[s], icmp, .. and many many more!)
> b) "transit" subinterface - ::: IP traffic ::: entered and left from the
> router, BUT only packets which are ::process-switched:: (ciscoDoc example:
> nonterminating tunnels)
> c) "cef-interface" subinterface - my understanding is that this interface
> is
> used for packets which the router guess to be CEF switched, but after L2
> deencapsulation it found out that they are non-IP packets so they must be
> process switched (when he finds in L2 payload an ARP packet, or L2
> keepalive,
> or IPX packet, ... anything with Ethernet II Type field different from
> 0x0800
> (IP) and 802.3 ethernet not carrying IP such as CDP)
>
> I hope I helped. Anyone - please comment if I am wrong. Thanks!
>
> Regards,
> Miroslav Kosut
>
> On Jan 2, 2010, at 10:49 PM, hopalong wrote:
>
> > Hi
> >
> > Can anyone help me with a *nice* explanation of the 3 subinterfaces
> > (CEF/Host/Transit) in terms of describing or rather working out which
> > traffic goes to which interface from the question!
> >
> > For instance if a CCPr question said something like 'Set the queue-limit
> for
> > input HTTP packets to 400 packets and limit the packet rate to 10 per
> > second' - would this be Host or Transit and why?
> >
> > Thank you!
> >
> >
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Received on Sun Jan 03 2010 - 14:26:13 ART