The server should not send the lease to expire time to the client. When the server received these messages will respond with DHCPACK (unicast) with the configuration parameters. The client sends these messages asking for some other configuration parameters. These messages are sent in broadcast fashion (unicast if the client knows about the DHCP server) when a client has configured with IP address with some other means like manually. RELEASE message is sent in unicast fashion. When this message is received at the server it will mark that IP address as not allocated however the server will retain the record of client parameters if in case client want to reuse the same address when sending new requests. This is to release the lease which is related to the Client ID field. This type of message is sent from the client to the server stating that the client has done using this IP address and it wants to give up. Also, if Server receives 2 DHCP REQUEST packets from the same client then for one request client will respond normal and NACK for other.When a client requests an invalid, for example, the client has moved to different/new subnet.The requested IP address is already allocated.Should start the discovery process again. If client receives a NACK it should use its remembered IP address and Will unicast to the relay agent IP address as unicast mentioned in the giaddrįield. The client is in same subnet and will broadcast the NACK message otherwise it Now If the giaddr field is empty, then server assumes that The client REQUEST message in that case it sends the DHCPNACK message. Something it may happen when server is not able to satisfy Then save the binding for that client to be in persistence state in the storageĪnd then will send DHCP ACK message which is again a unicast.Īny of the configuration parameters in the DHCPACK should not get conflict with the earlier OFFER message to which the client is responding. The server which is selected in the REQUEST message will The servers will receive the REQUEST message from the clientĪnd will check which server is selected from the Server ID filed and if theyĪre not on the list then those servers will use this as notification that client Below is a screenshot of Renew and ACK.Īs you can see the time the REQUEST is sent at 1 hour interval highlighted in red boxes. Usually, the lease time initially given by the server to the client is 24 hours (however it depends on the platform as in my case its 2 hours) and the renew is done when the half time of the lease is reached means if lease is 2 hours the renew will be done at 1 hour. LAN who had offered the IP address to the client on the OFFER message shouldĬlear the stored configuration offer to the client from the memory.Īlso, the REQUEST message is used to renew the lease time of the client IP address. The client sends this as broadcast so that all servers on the The requested IP address must the one which is seen in the yiaddr field of the OFFER message. The client will broadcast the REQUEST message and will populate the DHCP Server ID field with the IP address of the DHCP server to indicate which server it has selected to get an IP address and parameter configuration from. As we know client may receive multiple OFFER message from servers however if will choose only one server from which it will send the request to for configuration parameters.