Bug: Client flapping between VLANs when device has multiple IPs (same MAC)
Hi all,
I’m observing a reproducible issue with client detection in Omada SDN when a single device (in my case a NAS) is configured with multiple IP addresses across different VLANs.
Setup:
- Omada SDN Controller
- 3 VLANs:
- VLAN 0 (Default): 192.168.0.0/24
- VLAN 10(X) : 192.168.10.0/24
- VLAN 20(Y) : 192.168.20.0/24
- NAS with interfaces/IPs in all three networks:
- 192.168.0.2
- 192.168.10.2
- 192.168.20.2
- NAS connected via trunk port (tagged VLAN 10/20, untagged default / Native=Default
Observed behavior:
In the Omada Controller, the NAS is constantly “reconnecting” and switching between networks:
Example log pattern:
- Connected to Default (192.168.0.2)
- Connected to X (192.168.20.2)
- Connected to Y (192.168.10.2)
→ repeating every few minutes
This creates:
- Continuous “connect/disconnect” events
- Incorrect or unstable network assignment in the UI
Important:
- Network connectivity itself is stable
- No packet loss or real disconnects
- No STP events or MAC flapping on switch ports
- Same MAC address is used across VLAN interfaces (expected behavior for this device)
Expected behavior:
- Either:
- The client should be shown once with multiple IPs across VLANs, or
- Separate logical entries per VLAN/IP should be stable
- No continuous reconnect events if the physical link is stable
Actual behavior:
- Controller seems to reassign the same MAC to different VLANs repeatedly
- Appears as frequent reconnects (“flapping”), although no real link change occurs
Log
04-26-2026 09:25:24.887 INFO [client-inform-work-group-1] [] c.t.s.o.c.d.m.h.k(): Need override old client history for client 00-E0-4C-68-00-A1 with lastSeen 1777188295217
04-26-2026 09:24:54.897 INFO [client-inform-work-group-0] [] c.t.s.o.c.d.m.h.k(): Need override old client history for client 00-E0-4C-68-00-A1 with lastSeen 1777188265197
04-26-2026 09:27:54.968 INFO [client-inform-work-group-0] [] c.t.s.o.c.d.m.h.k(): Need override old client history for client 00-E0-4C-68-00-A1 with lastSeen 1777188445277
04-26-2026 09:28:24.986 INFO [client-inform-work-group-1] [] c.t.s.o.c.d.m.h.k(): Need override old client history for client 00-E0-4C-68-00-A1 with lastSeen 1777188475297
@Vincent-TP The reason that i want an own IP adress in each vlan is to fully make use of protocols which use Multicast/Broadcast like SSDP.
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these ips are switching continuesly
Hi @pustekuchen
Thanks for the information.
So the Omada controller is installed on the NAS, right?
I suspect this is the cause of the situation.
Is the NAS the only client encountering this situation? To confirm this, please test like below:
Plug another client into the switch port 8, and check if the same logs appear or not.
In the meantime, I will confirm this internally.
