CEF NoteBook

CEF:

Router Processor 

Fast switching - First packet routed by RP 

1960-IOS12.0 -> CEF(topology base forwarding)

-feature in routers without cpu utilization 

CEF Table:(stored in router memory) 

-Adjacency - L2 Info need to rewrite

-ARP Change Adjacency table

-Contain L2 rewrite Information

-each ARP entry have an entry in Adjacency table:

-show adjacency details: Hash-> srcMAC-DstMAC-Protocol(0x800 or IP),Out Interface

-Adjacency table don’t need aging time cause ARP aging time when remove an entry in the ARP, Router Processor remove that entry in Adj

-FIB - L3 Info need to lookup

-Information for making forwarding decision 

-Routing Table Change FIB

-CEF Mode:

-Centralize 

-no Line Card exist

-All process executed in Supervisor card

-Distributed 

-dCEF enabled on some switches like 6500,12000SW 

-Control Plan in the Supervisor 

-Create FIB and Adjacency table and sync them to line cards 

-Control Plan have independent Functionality 

-Communication type of Router CPU and Line cards is IPC(One of method communicate CPUs to each other )

-Data-Plan in other Cards

-

some Packet do not support by hardware switching like:

-ip packet with option in header(TOS)

-destination or src packet is tunnel interface

-packet need fragmentations 

Commands:

-show ip cef

-show adjacency

-show ip inter f0/0

-show cef is enabled or not

-(conf) no ip cef #disable cef on router

-(configure-if)no ip route-cache cef #disable cef on one interface

-(configure-if) no ip route-cache #set interface be in router process mode