Synonyms for dhcpoffer or Related words with dhcpoffer
Examples of "dhcpoffer"
A DHCP client may request more information than the server sent with the original
. The client may also request repeat data for a particular application. For example, browsers use "DHCP Inform" to obtain web proxy settings via WPAD.
When a DHCP server receives a DHCPDISCOVER message from a client, which is an IP address lease request, the server reserves an IP address for the client and makes a lease offer by sending a
message to the client. This message contains the client's MAC address, the IP address that the server is offering, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.
The DHCP operation begins with clients broadcasting a request. If the client and server are on different subnets, a DHCP Helper or DHCP Relay Agent may be used. Clients requesting renewal of an existing lease may communicate directly via UDP unicast, since the client already has an established IP address at that point. Additionally, there is a BOOTP flag the client can use to indicate in which way (broadcast or unicast) it can receive the
: 0x8000 for broadcast, 0x0000 for unicast. Only hosts with preconfigured IP addresses can receive unicast packets so in the usual use case clients in discovery phase should set BOOTP flag to 0x8000 (broadcast).
After parsing a PXE enabled DHCP server
, the client will be able to set its own network IP address, IP Mask, etc., and to point to the network located booting resources, based on the received TFTP Server IP address and the name of the NBP. The client next transfers the NBP into its own random-access memory (RAM) using TFTP, possibly verifies it (i.e. UEFI Secure Boot), and finally boots from it. NBPs are just the first link in the boot chain process and they generally request via TFTP a small set of complementary files in order to get running a minimalistic OS executive (i.e. WindowsPE, or a basic Linux kernel+initrd). The small OS executive loads its own network drivers and TCP/IP stack. At this point, the remaining instructions required to boot or install a full OS are provided not over TFTP, but using a robust transfer protocol (such as HTTP, CIFS, or NFS).
DHCP is used to provide the appropriate client network parameters and specifically the location (IP address) of the TFTP server hosting, ready for download, the initial bootstrap program (NBP) and complementary files. To initiate a PXE bootstrap session the DHCP component of the client's PXE firmware broadcasts a DHCPDISCOVER packet containing PXE-specific options to port 67/UDP (DHCP server port); it asks for the required network configuration and network booting parameters. The PXE-specific options identify the initiated DHCP transaction as a PXE transaction. Standard DHCP servers (non PXE enabled) will be able to answer with a regular
carrying networking information (i.e. IP address) but not the PXE specific parameters. A PXE client will not be able to boot if it only receives an answer from a non PXE enabled DHCP server.
Copyright © 2017