Description DHCP packet type
1, when the DHCP Discover DHCP client requests an address, the DHCP server does not know the position, so DHCP client broadcasts a request packet transmitted within the local network, the packet becomes Discover packet object is found in the network DHCP server, all incoming packets discover DHCP server will send a response packet, DHCP client can know the position accordingly present in the network DHCP server.
2, after the DHCP Offer DHCP server receives Discover packet, it will look for a suitable ip address in the address configured in the pool, plus the corresponding period of the lease and other configuration information (gateway, DNS servers, etc.), a construction Offer messages sent to customers to inform users of the server can provide IP addresses. (Just tell the client can provide, is pre-allocated, but also through the ARP client detects whether the IP repeat)
3, DHCP Request DHCP client receives a lot of Offer, these must be chosen in a response. Client server usually choose the first response message Offer as their target servers, and to respond to a Request message broadcast server selected notifications. After the DHCP client successfully obtained an IP address, the address you used the last 1/2 of the lease, the DHCP server will send a unicast Request packet renewed leases, if the DHCP ACK packet is not received in the past three lease / 4:00, send broadcast messages Request to renew the lease.
4, DHCP ACK DHCP server receives a Request message, the user carries the MAC Request message to find the corresponding renewal has not recorded, if the ip address is sent as a response ACK message, it informs the user using the assigned .
5, DHCP NAK if DHCP server receives the Request packet, records are not found lease or for some reason can not allocate ip address is normal, sends an ACK packet response, notifying a user can not assign the appropriate ip address.
6, DHCP Release when the user is not required to use the allocation ip address, it will send a Release message to the DHCP server, users no longer need to tell the server assigned ip address, the DHCP server will release the lease be bound.
7, DHCP Decline DHCP client receives the ACK packet DHCP server response by address conflict conflict detection discovery server address assignment or for other reasons can not be used, then send Decline message notification server assigned ip address is not available use.
8, DHCP Inform DHCP client if required to obtain from the DHCP server more detailed configuration information, send an Inform message request to the server, the server receives the message, according to the lease will look to find the appropriate configuration information after sending ACK packet to respond to DHCP clients (rarely used).