show ip dhcp conflict
To display address conflicts found by a Cisco IOS Dynamic Host Configuration Protocol (DHCP) Server when addresses are offered to the client, use the show ip dhcp conflict EXEC command.
show ip dhcp conflict [address]
This command first appeared in Cisco IOS Release 12.0(1)T.
The server detects conflicts using ping. The client detects conflicts using gratuitous Address Resolution Protocol (ARP). If an address conflict is detected, the address is removed from the pool and the address will not be assigned until an administrator resolves the conflict.
The following example displays the detection method and detection time for all IP addresses the DHCP server has offered that have conflicts with other devices. Table 3 lists descriptions of the fields in the example.
Router> show ip dhcp conflict
IP address Detection Method Detection time
172.16.1.32 Ping Feb 16 1998 12:28 PM
172.16.1.64 Gratuitous ARP Feb 23 1998 08:12 AM
Table 3 show ip dhcp conflict Field Descriptions
clear ip dhcp conflict
ip dhcp ping packets
ip dhcp ping timeout