When would DHCP conflicts happen?

johnifanx98

According to CCNA study guide describes, before assigning an IP to the work stations, the DHCP server will ping to verify the IP is avail. And, the work station will ARP to verify the address validity. The whole process looks pretty secure to avoid the conflicts. So, any TYPICAL scenario where IP addr conflicts will occur?

zrockstar

There may be a host out there operating under a static IP address that hasn't been taken out of the DHCP pool. Also, a DHCP service may have come online while hosts still have old active leases from another service, and have not gone through an ipconfig release/renew.

JDMurray

Conflicts will occur when there is a purposeful or accidental misconfiguration in the network addressing scheme.

johnifanx98 wrote: »

before assigning an IP to the work stations, the DHCP server will ping to verify the IP is avail.

A host that has been assigned an IP address that's in a DHCP pool may not be online when the DHCP server pings.

kurosaki00

Usually what JD said
someone miss configured something
You can get stuff like:
You have 2 hosts that are supposed to be in the same network and use the same DHCP server but one host got a wrong DHCP server address configured in it

Ltat42a

One instance I can think of is a network printer that has a static address from the pool, and was left out of the excluded range.

MAC_Addy

Best practice that I've found when trying to avoid DHCP conflicts is to create your pool of DHCP addresses 192.168.1.100 through .200. You can use 192.168.1.1 through .99 and 192.168.1.101 through .254 for static addressing. That's if you're using a /24 subnet. If you're not, then use a DHCP pool that's most appropriate for your network.

zrockstar

kurosaki00 wrote: »

You have 2 hosts that are supposed to be in the same network and use the same DHCP server but one host got a wrong DHCP server address configured in it

Gratuitous ARP is not going to fix the fact that a host has the wrong DHCP server address in it.