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ARP broadcast storm: Information and Effects

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Applies to

  • ONTAP 9 
  • Clustered Data ONTAP

Description 

What is the following event reported on /mroot/etc/log/ems and what can be the impact?

Example:

"[XXXXXX: NwkThd_0X netif.rateLimitThreshold:error]: High rate limit on the network interface e0* for broadcast protocol ARP is detected"

Answer

  • This message is an indication of an incoming ARP broadcast storm.
    • It is generated from a process that monitors the inflow and indicates us in case of any unusual events.
    • The interface received a very high number (>5000 in this case) of ARP broadcast packets in the last second of monitoring.
    • The system also follows a discarded window of half a second (500 ms) just after this to cool off a bit.
      • Note: This message occurs when the protocol rate threshold is reached on a network interface.
  • Corrective Action:
    • Fix the faulty network configuration or incorrect setup that enables a sudden spike in broadcast packets to bring down the node.

Additional Information

  • Historically, these kinds of storms are generated due to network mis-configuration like a loop or a misbehaving network device.
  • Check for any such activities around the same time-frame on the devices that are connected to the same broadcast domain of those ports.
  • In some situations, these ARP storms can lead the system to be unresponsive or eventually to disruption as they can exhaust the network resources.
  • Capturing a packet trace on the concerned interface can be helpful to pinpoint the device causing the large amount of ARP broadcast packets
  • How to capture packet traces on ONTAP 9.10+ systems

 

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