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Webcast-Catalyst9k
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Order that packets are processed coming into an interface

Hi, I was wondering in what order technologies process packets on an interface as they come in or go out.  For instance, when a packet comes in an interface it is processed by route maps, buffers, QoS, NBAR, access-lists, NAT, MPLS, Zone Based Firewalls, CIF, routing, and numerous other technologies if they are configured.  Is there something on Cisco’s web site (or elsewhere) that describes this?  I am hoping to see something as detailed as possible.  Also, does this apply to both routers and switches when processing packets.

For example, when troubleshooting I would like to look at this list and imagine a packet as it comes in an interface, is buffered, is processed by QoS, passes though NAT, is allowed to pass from one zone to another via a ZBF, and is processed going out a an interface to its destination host.  This might be helpful in figuring out at what point a certain technology is causing the problem.  Thanks for your help.

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VIP Purple

Order that packets are processed coming into an interface

The typical google-search-string for that is "NAT order-of-operation". The best page I ever found on that is the following:

http://etherealmind.com/cisco-ios-order-of-operation/

(very good blog btw ... :-) )

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Cisco Employee

Order that packets are processed coming into an interface

Hello Patrick,

I have found these documents to be useful even though probably not entirely exhaustive:

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080133ddd.shtml

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a0080160fc1.shtml

Best regards,

Peter

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