Sunday, February 1, 2015

Cisco CCNP - 300-101 - Cisco CEF

So it's that time again for me to renew my Cisco Certifications. As a result, this post will be based on my preparation for the CCNP Route Exam (300-101).

In this post I will be focusing on Cisco CEF

Router planes
    - Management Plane
        Used for device management SSH, Telnet, HTTPS, etc
    - Control Plane
        - Used for making forwarding decisions. Used by routing protocols
    - Data Plane
        - Used for forwarding data
   
    - Control and data plane influcence how fast traffic can pass through a router
   

Cisco Packet switch modes
    - Process switching
        - Routing of packets
        - CPU becomes involved
        - Process switching is enabled by disabling fast switching using "no ip route cache"
   
   
    - Fast switching
        - Dramatically reduces CPU utilzation
        - Fast switching uses fast cache
        - Fast cache is found on the data plane
               
       
    - Cisco Express Forwarding  (CEF)
        - maintains two tables in the data plane
            - FIB - maintains layer 3 information
            - adjacency - maintains layer 2 information
        - The above tables are populated from the IP routing table and ARP cache
        - Does not require the first packet to be processed switch
        - entire flow can be forwarded at the data plane
        - Enabed by default
        - use "ip cef" to enable CEF globally
        - can be enabed on the interface by "ip route-cache cef"
       
       
        - if output states "attached" the network is directly attached
        - if output states "receive" the entry is an IP address on the router interface


Policy Based Routing (PBR)
    - Overrides the default destination based forwarding
    - operates before the CEF table gets involved
    - uses route map (uses access list)
    - verify config using   
        - show ip policy
        - show route-map
        - "default" keyword tells PBR to try default logic which is destination first. Only use PBR when default fails
       


References:
CCNP official Cert Guide - CCNP Routing and Switching - Route 300-101
http://www.cisco.com/c/en/us/td/docs/ios/12_2/switch/configuration/guide/fswtch_c/xcfcef.html
http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/17812-cef-incomp.html

1 comment:

  1. Thank you for sharing. Your blog has given me that thing which I never expect to get from all over the websites. Nice post guys!

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