mpls and cef

Unanswered Question
May 7th, 2009

Hi all

if we are using cef on the routers, is this not the same kind of thing as mpls or do they do different things ?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)

Multi-Protocol Label Switching (MPLS) is a WAN transport protocol (think Frame-Relay, ATM, etc.) used by Service Providers. That's about as simple as I can make it.

Cisco Express Forwarding (CEF) is a Cisco proprietary technology for speeding up the switching paths in your router. It can also be used as a load balancing mechanism.

The simplest way I can explain it is this. Imagine yourself on a family trip with each of your family in a different vehicle. You all are headed to same destination. You are the lead driver. All of the other driver's follow your lead.

MPLS is the road you are driving on.

CEF is kinda like the drivers following you. They don't need the directions, they can just follow you. CEF speeds up the entire conversation, because not every packet needs to be process switched (inspected for source & destination).

Please rate if this was helpful....

carl_townshend Thu, 05/07/2009 - 06:42

Hi there

I thought mpls was for speeding up the paths also? i thought it was so that there is no need for a routing table lookup, it simplly looks in the header at the label and sends it out an interface, which is faster.


how does cef know that the next packetis part of the same flow ?

I thought the way it worked was this:

It takes the first packet's Source IP address and PORT number, destination IP and port number, then hashes that information.

The next packets in the flow (before it times out) get fast switched. It hashes the packets and does a compare to forward the information.

MPLS is a way of separating traffic on a shared medium. AT&T can buy large circuits that feed many customers. How do you keep that information secure? MPLS helps with that. MPLS is a layer 2 to layer 3 PROTOCOL that is a way for providers to encapsulate traffic. I think that MPLS allows the providers to provide a single way of encapsulating traffic no matter the physical or data link layers.

CEF is a Cisco technology that runs on Cisco Routers to speed up the "Processing/Routing/Switching" of packets. CEF doesn't encapuslate packets.


This Discussion