7600 CEF table

Unanswered Question
Feb 5th, 2009


How OSM and Enhanced Flexwan access the CEF table on 7600? If they use the PFC3 or have they own?

The reason is they are not having DFC by default but still have local FIB/CEF table. What is purpose of this ??



I have this problem too.
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Mohamed Sobair Thu, 02/05/2009 - 07:50


Packet forwarding/Switching is acomplished by the following:

1- ASIC: (Application Specific Integrated Circuit), here the hardware is correctly programmed to perform packet Switching.

2- Procees Switching table: all Packets has to be forwarded to the CPU , the CPU then performed the Switching based on router IP lookup table .

3- Fast Switching table: This table is created on demand and stores most recent routes in a Route cache.

4- CEF: Cisco Express forwarding is developed to improve/enhance the traditional IP Lookup which is done on Software bases, The rip table is copied into the CEF table as soon as the router starts up.

CEF table Consisit of the following:

a) FIB (Forward Information base) : this contains the IP prefix(destination) + nexthop address + exit Interface (ARP table)

B)Adjacency Table: This table stores the Layer-2 header.



chintan-shah Thu, 02/05/2009 - 08:06

Hi Mohamed,

Yes, we use CEF only on our 7600 but question i had was, we see same CEF on Enhanced FlexWAN and OSM card ( they don't have DFC). so will forwarding on Flext WAN will be locally or central forwarding through PFC ?


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