no ip dhcp conflict address [ip]
Use this command to clear a specific IP address from the DHCP conflict table, allowing the DHCP server to reassign that address to a client.
no ip dhcp conflict address [ip]When to Use This Command
- After resolving a duplicate IP address issue, clear the conflict entry so the address can be reused.
- When a statically assigned device is moved or reconfigured, remove its IP from the conflict table.
- During network troubleshooting, clear a conflict entry to test if the address is now available.
- After fixing a misconfigured device that caused a conflict, remove the conflict record to restore normal DHCP operation.
Command Examples
Clear a single IP address conflict
no ip dhcp conflict address 192.168.1.100This command removes the IP address 192.168.1.100 from the DHCP conflict table. No output is displayed if successful. Use 'show ip dhcp conflict' to verify the entry is gone.
Clear all DHCP conflicts
clear ip dhcp conflict *This command clears all entries from the DHCP conflict table. No output is displayed. Use 'show ip dhcp conflict' to confirm the table is empty.
Understanding the Output
The 'no ip dhcp conflict address' command does not produce any output on success. To verify the result, use 'show ip dhcp conflict' which displays a table with columns: 'IP address' (the conflicting IP), 'Detection method' (how the conflict was detected, e.g., Ping or Gratuitous ARP), 'Detection time' (timestamp of detection), and 'VLAN' (VLAN ID if applicable). A clean conflict table indicates no conflicts; any remaining entries need investigation.
CCNA Exam Tips
CCNA exam expects you to know that DHCP conflicts are detected via ping or gratuitous ARP, and that clearing conflicts is done with 'clear ip dhcp conflict *' or 'no ip dhcp conflict address <ip>'.
Remember that 'no ip dhcp conflict address' is a global config command, not an exec command. You must be in global configuration mode.
The exam may test that after clearing a conflict, the DHCP server can reassign the address immediately if it is still in the pool and not excluded.
Be aware that 'clear ip dhcp conflict *' is an exec mode command, while 'no ip dhcp conflict address' is a global config command. Know the difference.
Common Mistakes
Mistake: Using 'no ip dhcp conflict address' in privileged exec mode instead of global config mode. Consequence: Command not recognized.
Mistake: Forgetting to verify with 'show ip dhcp conflict' after clearing. Consequence: Unaware that conflict still exists.
Mistake: Using 'clear ip dhcp conflict *' in global config mode. Consequence: Command not recognized; must be in exec mode.
Related Commands
ip dhcp excluded-address [start] [end]
Excludes one or more IP addresses from the DHCP pool so they are not automatically assigned to clients, typically used for static assignments like servers or routers.
show ip dhcp conflict
Displays IP address conflicts detected by the DHCP server, helping administrators identify and resolve duplicate IP assignments on the network.
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