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CISCO Load Balancing CEF

Posted on 2014-09-26
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Last Modified: 2014-09-30
Hi,

I have a quick question on CEF.  Once I configure CEF on the 2 interfaces that will be going to out to the web, do I configure 2 last resort routes.  For Example:

0.0.0.0 0.0.0.0 192.168.1.1 1
0.0.0.0 0.0.0.0 192.168.1.2 1

Thank you for your help in advance
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Question by:thomasm1948
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Expert Comment

by:Otto_N
ID: 40348682
Short answer: Yes. If you have two gateways to the Internet, you should configure two static routes.

Technically, CEF and last-resort routes doesn't really have anything to do with each other - You would have configured both static routes in any case, whether you used  CEF or not.
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Author Comment

by:thomasm1948
ID: 40350477
what would the benefit be, if I do not configure CEF.  Is there a better way to load balance between to ISPs?
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Accepted Solution

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Otto_N earned 500 total points
ID: 40351861
CEF switching is just a way to speed up the rate at which packets are switched - It use up a bit more memory resources (to build the forwarding tables required), but if your device have sufficient memory, CEF is recommended - It is by default enabled on the newer Cisco kit.

I must confess, I had to read up on the load balancing of CEF. Without CEF, traffic is usually forwarded round-robin (one packet to ISP-1, the next packet to ISP-2).  CEF, by default, load-balance per destination.  This result in a more  intelligent forwarding - packets from the same source to the same destination will be switched to the same ISP, where packets from the same source to a different destination might be switched to the other ISP.

While this can give you uneven utilization between the two uplinks (depending on your traffic profile), it will reduce the probability that packets are delivered out-of-order.
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Author Closing Comment

by:thomasm1948
ID: 40351969
thank you for all of your help
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