Chapter 2 Advanced Routing for FortiOS 5.0 : Advanced Static Routing : Advanced static example: ECMP failover and load balancing : Configuring spillover or usage-based ECMP : Determining if an interface has exceeded its Spillover Threshold
  
Determining if an interface has exceeded its Spillover Threshold
You can use the diagnose netlink dstmac list CLI command to determine if an interface is exceeding its Spillover Threshold. If the command displays over_bps=1 the interface is exceeding its threshold. If over_bps=0 the interface has not exceeded its threshold.
dev=Wifi mac=00:00:00:00:00:00 src-vis-os src-vis-host src-vis-user rx_tcp_mss=0 tx_tcp_mss=0 overspill-threshold=0 bytes=0 over_bps=0 sampler_rate=0