I have a situation like this:
- Isolated Gigabit Ethernet LAN with a handful of Linux boxes and Macs on it
- Airport Extreme wireless access point is also connected to the LAN
- Two iPads talking to the system via the Airport Extreme and Wifi
- The iPads are set to use static IP address settings. One iPad is set to IP address 192.168.8.38 and the other is set to 192.168.8.39.
- One of the Linux boxes periodically runs arp-scan and reports if any duplicate IP addresses are present on the LAN.
The issue is that sometimes (not always), the arp-scan process will report that both iPads' MAC addresses are using the same IP address. When this happens, arp-scan's output shows both iPad's MAC addresses associated with IP address 192.168.8.39. (This despite us manually verifying that the two iPads have distinct IP addresses and MAC addresses by looking at their network settings pages on-screen)
Other than this report from arp-scan, communication with the iPads appears to work fine.
Does anyone know what might cause this behavior? All I can think of is that the iPads' MAC addresses might be hashed to the same value somehow and thus they are overwriting each other in some data structure... or that the iPad set to address 192.168.8.38 occasionally "wanders over" and uses the address next door instead, despite being set to a static IP address. Neither of those hypotheses seems very likely to me though. :^(