Multilink PPP or CEF

Posted on 2005-05-09
Last Modified: 2012-05-05
I'm currently using multilink ppp to bond 5 T1 circuits between a 3825 and a 3725 router. I have read discussions of IP CEF providing improved performance. How much peformance gain if any would there be if one was to use CEF with these routers? Can CEF be applied to the serial interfaces while still using mlppp? Can CEF be used with static routing? My mlppp is working fine but looking for the most efficient way to bond the circuits. A config example of how to setup cef would be appreciated. Please advise.
Question by:setags
    LVL 13

    Expert Comment

    to use CEF, you just enable it globally:

    Router# config t
    Router(config)# ip cef

    if you are using distributed MLPPP, simply put the work "distributed" after your "ip cef"

    This discussion of CEF:

    suggests that you would use it when you have a large number of traffic going to multiple destinations, such that the routing entries would not be in the route-cache. Thus using CEF would decrease the time for route lookups. It really depends on your traffic patterns and routes as to whether you will gain any benefit from it. If you have enough memory in the routers, you can turn it on and see what happens, it shouldn't cause anything to be slower.

    Author Comment

    In my network configuration I have only two locations connected together via 5T1's bonded (mlppp). It sounds doubtful that I would see any noticeable performance gain if CEF benefits networks with distributed routes. Any thoughts?
    LVL 13

    Accepted Solution

    Exactly, if the routes aren't being pushed out of the cache, then you shouldn't see any benefit from CEF. The only time it might help is if you have very high CPU usage on the router. Using CEF might allow you to trade some CPU usage for a little additional memory usage (obviously you would only do this if you have memory to spare).

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    How to run any project with ease

    Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
    - Combine task lists, docs, spreadsheets, and chat in one
    - View and edit from mobile/offline
    - Cut down on emails

    This article is a guide to configure bridging on Cisco Routers.  This is something I never knew was possible until after making a few phone calls to Cisco.  Using bridging saved our company money by not requiring us to purchase a new switch.  Bridgi…
    We've been using the Cisco/Linksys RV042 for years as: - an internet Gateway - a site-to-site VPN device - a leased line site-to-site subnet-to-subnet interface (And, here I'm assuming that any RV0xx behaves the same way as an RV042.  So that's …
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

    759 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    11 Experts available now in Live!

    Get 1:1 Help Now