Dell N3200-ON Networking N-Series Switches CLI Reference Guide version 6.8.0 - Page 571

For each device entry in the IPDT table, ARP probe is sent periodically to check the reachability of the device. If there are no ARP responses received for the configured number of retransmit ARP probes, the device entry is marked inactive. IPDT does not send ARP probes for entries already present in the ARP table until they age out and ARP packets are exchanged. When IPDT is enabled for the first time, it may take up to 20 minutes (or the configured ARP timeout) for the IPDT table to populate. IPDT is supported for physical (Ethernet) interfaces and for port-channels. IPDT configuration for Ethernet interfaces is ignored for interfaces which are part of a port-channel. Configure IPDT on the port-channel instead. An ARP probe is transmitted on the physical port or port-channel in the VLAN associated with the device in the IPDT table, with the following fields set: a The source MAC address is set to the L3 interface MAC on routed VLANs and to the L2 interface MAC on switched VLANs. b The destination MAC is set to device entry MAC address. c On L3 routed VLANs, the source IPv4 address is set based on the matching IPv4 subnet on the VLAN interface if it exists or else it is set to 0.0.0.0. On L2-only switched VLANs, the source IPv4 is set to 0.0.0.0. d The target IPv4 address is set to the IP address of the device entry. The probe retransmit interval is configurable, with a default value of 30 seconds. The first probe timeout for each device entry is sequentially distributed from 1 sec to the probe-retransmit-interval value. This is done for pacing the number of probes that are sent out every second, for performance reasons. When an interface transitions to the forwarding state, an ARP probe is sent for all the interface device entries. To avoid duplicate IP conflicts, transmission of the initial ARP probe is delayed by the probe delay interval after the interface transitions to the forwarding state. It is possible that a DHCP client may obtain a DHCP lease before the interval expires. Layer 2 Switching Commands 571