Chapter 9 High Availability for FortiOS 5.0 : HA and failover protection : Cluster virtual MAC addresses : Diagnosing packet loss with two FortiGate HA clusters in the same broadcast domain : Ping testing for packet loss
  
Ping testing for packet loss
If the network is experiencing packet loss, it is possible that you will not notice a problem unless you are constantly pinging both HA clusters. During normal operation of the network you also might not notice packet loss because the loss rate may not be severe enough to timeout TCP sessions. Also many common types if TCP traffic, such as web browsing, may not be greatly affected by packet loss. However, packet loss can have a significant effect on real time protocols that deliver audio and video data.
To test for packet loss you can set up two constant ping sessions, one to each cluster. If packet loss is occurring the two ping sessions should show alternating replies and timeouts from each cluster.
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