Introduction To Bootp Client - H3C S3100-52P Operation Manual

Operation Manual – DLDP
H3C S3100-52P Ethernet Switch
DHCP server. The packet contains the IP address carried in the DHCP-OFFER
packet the DHCP client receives.
Acknowledgement. Upon receiving the DHCP-REQUEST packet, the DHCP
server that owns the IP address carried in the DHCP-REQUEST sends a
DHCP-ACK packet to the DHCP client. The packet contains the IP address offered
and other configuration information. The DHCP client binds TCP/IP protocol
components to its MAC address after receiving the packet.
IP addresses offered by other DHCP servers (if any) through DHCP-OFFER packets
but not selected by the DHCP client are still available for other clients.
2) The DHCP client accesses the network for the second and the followed time
In this case, the DHCP client establishes connections with the DHCP server through
the following steps.
After accessing the network successfully for the first time, the DHCP client can
access the network again by broadcasting a DHCP-REQUEST packet that
contains the IP address assigned to it last time instead of a DHCP-DISCOVER
packet.
Upon receiving the DHCP-REQUEST packet and, when the IP address applied by
the client is available, the DHCP server that owns the IP address responds with a
DHCP-ACK packet to enable the DHCP client to use the IP address again.
If the IP address is not available (for example, it is assigned to another DHCP
client), the DHCP server responds with a DHCP_NAK packet, which enables the
DHCP client to request for a new IP address by sending a DHCP-DISCOVER
packet once again.
3) The DHCP client extends the lease of an IP address
IP addresses assigned dynamically are only valid for a specified period of time and the
DHCP servers reclaim their assigned IP addresses at the expiration of these periods.
Therefore, a DHCP client need to extend the lease period if it is to use a dynamically
assigned IP address for a period longer than allowed.
By default, a DHCP client updates its IP address lease automatically by sending
DHCP-REQUEST packets to the DHCP server when half of the lease period expires.
The DHCP server, in turn, responds with a DHCP-ACK packet to notify the DHCP client
of the new lease if the IP address is still available. An S3100-52P switch operating as a
DHCP support this lease auto-update process.

3.2 Introduction to BOOTP Client

A BOOTP client can request the server for an IP address through BOOTP. It goes
through the following two phases to apply for an IP address.
Sending a BOOTP request packet to the server
Processing the BOOTP response packet received from the server
Chapter 3 DHCP/BOOTP Client Configuration
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