Quick troubleshooting view
Two devices use the same IP address, resulting in loss of connectivity, ARP switches and intermittent access.
- static address within a DHCP range
- former DHCP reservation
- or VM with copied configuration
- Identify the IP in conflict
- Compare the MACs
- Control DHCP
- remove static IPs from DHCP range
- create a clean reservation if necessary
- correct the equipment configured in duplicate
Contextual technician plan
Please identify the exact address, address and schedule of the problem.
a/C/00/Add.1The command should complete without an unexpected error and return data consistent with the intended service.
If the result is normal, keep this layer lower in the hypothesis ranking and continue with the next discriminating check.
If the result is abnormal, preserve the output and investigate this layer before making broader changes.
Check the ARP or the switch tables to find the equipment concerned.
ipconfig /all.A valid non-APIPA
The local IP configuration is coherent; test the next network layer.
Investigate DHCP, VLAN, adapter configuration, gateway or DNS assignment.
Check reservations and the DHCP extension.
Well-NetNeighbor -AddressFamily IPv4The command should complete without an unexpected error and return data consistent with the intended service.
If the result is normal, keep this layer lower in the hypothesis ranking and continue with the next discriminating check.
If the result is abnormal, preserve the output and investigate this layer before making broader changes.
Control servers, printers, hypervisors and network equipment.
“Search for static IPs” should produce an observation that clearly confirms or rules out “equipment manually configured with an IP already used”.
If the observation is normal, lower “equipment manually configured with an IP already used” in the ranking and continue with the next distinct check.
If the observation is abnormal, keep the evidence and investigate “equipment manually configured with an IP already used” first. Related action: purging ARP entries after correction if problem persists.
Repeat the same validation test after the correction and confirm the original symptom is gone. Validate stability before closing the incident.
Before changing configuration, record the current value and a way back.
Escalader if the address changes regularly from Mac, which may indicate cloned equipment, HA problem or more complex network configuration.
Two devices use the same IP address, resulting in loss of connectivity, ARP switches and intermittent access.
Causes probables
- static address within a DHCP range
- former DHCP reservation
- or VM with copied configuration
- equipment manually configured with an IP already used
Diagnostic étape par étape
- 1
Identify the IP in conflict
Please identify the exact address, address and schedule of the problem.
- 2
Compare the MACs
Check the ARP or the switch tables to find the equipment concerned.
- 3
Control DHCP
Check reservations and the DHCP extension.
- 4
Search for static IPs
Control servers, printers, hypervisors and network equipment.
Commands utiles
a/C/00/Add.1ipconfig /all.Well-NetNeighbor -AddressFamily IPv4Solutions possibles
- remove static IPs from DHCP range
- create a clean reservation if necessary
- correct the equipment configured in duplicate
- purging ARP entries after correction if problem persists
Escalader if the address changes regularly from Mac, which may indicate cloned equipment, HA problem or more complex network configuration.