Symptoms

When an IP address moves to another node, the new node that receives the IP address may not be reachable. Connections to the node drop, and the node remain unpingable. 

Cause

A PowerScale node sends a GARP in order to update the switch and all other devices on the network of the change. The GARP allows these devices to update their Address Resolution Protocol (ARP) tables with the new IP to Media Access Control (MAC) address. If all the following conditions are met, the GARPs do not pass through the switch. Flooding mode is disabled.GARP-based detection is disabled.Rogue-IP detection is disabled.Data-plane learning is enabled. No devices are aware of the change in MAC address relating to the IP that moves. Then all packets to that IP address are sent to the wrong device and ultimately dropped. The result is that clients that were communicating with that IP address no longer have connectivity to the node. Any sessions to that IP address are disconnected.NOTE: PowerScale requires that standard Layer 2 switching functionality is enabled in order to operate properly with a switch.

Resolution

There are three major components to this change: Enable - ARP FloodingEnable - GARP-based DetectionDisable - Rogue-IP DetectionDisable - Data-Plane Learning All four components must be changed for this to work properly.

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