Genie's Tech Blog

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CEF - Monitoring and Debugging

Hey Guys, Welcome back. Today I will continue my discussion on the old topic of Load Balancing and will discuss how to monitor and debug the CEF load balancing mechanism. A number of configurtion, exec and debug commands exist to monitor and debug the load balancing in a running system. We shall now see them one - by - one. 1. ip cef accounting load-balance-hash This configuration command enables the per hash packet counters which can be seen using the show ip cef <prefix> internal command. This command is supported on all the platforms that employ a software forwarding pat... [More]

CEF - The Polarization Effect

Hello Friends, In the last post we discussed about CEF Load Balancing. We also saw that per-destination based load balancing uses hash function to load balance the traffic. Since the hash function is used, it is very important that we also understand the concept of traffic polarization.  Consider a topology in which there are 4 paths in order to reach A0 to B0.   {R1, R2, R4}, {R1. R2, R5}, {R1, R3, R6} and {R1, R3, R7}. Now, considering R1, per-destination will assign the session from A0 to B0 to one of the two available paths {R1. R2} and {R1, R3}. Lets for this example we p... [More]

CEF Load-Balancing

Hello All, Today, I will be discussing some basic stuff about CEF (Cisco Express Forwarding) load balancing mechanisms and understanding how different algorithms are working. But, lets first start with defining what is load balancing. Load balancing is basically the ability to share the trafic to the destination IP prefix over all the active paths. CEF supports two methods of load balancing: 1. Per-packet load balancing 2. Per-destination load balancing We will now be discussing them one by one. Per-packet load balancing: Per-packet load-balancing works by using the availa... [More]