When does EIGRP Equal Load-Balancing happen

jskfan used Ask the Experts™
When does EIGRP Equal Load-Balancing happen

I have managed to Test Unequal load-balancing using Traceroute multiple times and quickly.

However for Equal Cost , I tried Traceroute multiple times and quickly , but it keeps going through one path..

I am not sure now if Equal Cost Load-balancing happens only when there is congestion on one path...if so why this does not happen on Unequal Cost..

Any Clarification will be very much appreciated.

Thank you
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Generally, there is nothing that need to be configured, but you can change default behavior (it should be per flow, not per packet). Default is to load balance up to 4 equal cost paths (sure, need to be present in routing table).
Depending on version of IOS by default ip cef is load balancing traffic including sourceIP-destinationIP (which will lead that the same path is always used), or universal algorithm (even if ports are included in algorithm it will not affect ICMP - no port present in packet).
To switch to universal algorithm in global configuration mode issue (if supported on device):
ip cef load-sharing algorithm universal
But it may still have the same end result. Since traffic is actually forwarded by ip cef.

Details regarding CEF
show ip cef
show ip cef details
show cef interface

And to check load balancing if ip cef is responsible for always using the same path - create few loopbacks configure IP addresses. Using different source IP address as source should lead to selecting different path to destination.


Thanks for the Info  ... I will revisit this topic later

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