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DHCPInform is a DHCP message used by DHCP clients to obtain DHCP options. While PPP remote access clients do not use DHCP to obtain IP addresses for the remote access connection, Windows 2000 and Windows 98 remote access clients use the DHCPInform message to obtain DNS server IP addresses, WINS server IP addresses, and a DNS domain name. The DHCPInform message is sent after the IPCP negotiation is concluded. The DHCPInform message received by the remote access server is then forwarded to a DHCP server. The remote access server forwards DHCPInform messages only if it has been configured with the DHCP Relay Agent..
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∙ 16y ago
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What message type is not used during a successful DHCP address assignment?
DHCPINFORM
Describe the steps taken by the client and DHCP server in order to obtain an IP address?
Firstly, a DHCP server is needed which distributes the IP addresses. This machine will serve as a base for all DHCP requests and must also have a fixed IP address. Therefore, on a network there can only be one machine with a fixed IP address, the DHCP server.The basic communication system is BOOTP (with UDP frame). When a machine is turned on, it has no information on its network configuration, and there is nothing special that the user needs to do to find an IP address. In order to do this, the technique used is the broadcast: to find and talk with a DHCP server, the machine will simply send a special broadcast packet (broadcast on 255.255.255.255 with other information such as the type of request, the connection ports, etc.) over the local network. When the DHCP receives the broadcast packet, it will send back another broadcast packet (do not forget that the client does not obviously have the IP address and that therefore cannot be connected to directly) containing all the information required for the client.It could be believed that one single packet is enough for the protocol to work. In fact, there are several types of DHCP packets likely to be issued either by the client for the server(s), or by the servers to a client:DHCPDISCOVER (to locate available DHCP servers)DHCPOFFER (server response to a DHCPDISCOVER packet, which contains the initial parameters)DHCPREQUEST (varied request from the client for example to extend its lease)DHCPACK (server response which contains the parameters and IP address of the client)DHCPNAK (server response to indicate to the client that its lease has expired or if the client announces a bad network configuration)DHCPDECLINE (the client announces to the server that the address is already in use)DHCPRELEASE (the client releases its IP address)DHCPINFORM (the client requests local parameters, it already has its IP address)The first packet issued by the client is a DHCPDISCOVER type packet. The server responds with a DHCPOFFER packet, particularly in order to submit an IP address to the client. The client establishes its configuration and then makes a DHCPREQUEST to validate its IP address (a broadcast request since DHCPOFFER does not contain the IP address). The server simply responds with a DHCPACK with the IP address for confirmation of the allocation. Normally, this is enough for the client to obtain an effective network configuration, but it can be longer or shorter according to whether the client accepts the IP address or not.Hope this will help you to understand DHCP.Regards,Jaydeep.Gatlewar@gmail.com
