DHCP conflicts

[Francisco Sanchez]

Hi 

What is the principal reason therefore occurs DHCP conflicts???

Is very continuos the problems with DHCP conflicts, all day I need clean the conflicts

Regards

[Bilal Nawaz]

Hello,

Do you mean IP address conflicts? i.e. two hosts having the same IP address? What is your DHCP server?

[e.ciollaro]

It happens because DHCP servers verifies if IP address are already in use before lease them to a client. If it is in use, DHCP server "froze" that IP.  Usually it happens because of statically assigned ip address that overlap DHCP pool. Your conflict is always on the same IP  ?   

enrico

[ALIAOF_]

I'm assuming you are talking about the "ip dhcp conflict logging".  Which then prevents the IP address from being reused unless you manually clear it.  Well you can disable that command or if you really need to keep it I have used EEM script in the past to clean it, something like this.  Can be used as a reference.

event manager applet CLEAR_DHCP_CONFLICT (This is applets name)
event timer watchdog time 172800 (Using the watchdog option I allowed it to run every 48 hours)
action 1.0 cli command “enable”
action 2.0 cli command “clear ip dhcp conflict *”
action 3.0 syslog msg “IP DHCP Conflict log has been cleared successfully” (syslog msg enabled me to trigger a syslog message)

[e.ciollaro]

Another way to avoid manual cleaning is the command:

ip dhcp conflict resolution interval min

This way the router periodically checks if IPs are still in conflict. If not remove the IP addresses form blocked IP.

Min range from 5 to 1440 minutes (24hours)

Bye,

enrico

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