Using The Switch As A Bootp/Dhcp Relay Agent; Dhcp Relay Agent Overview - Dell Force10 S2410-01-10GE-24P Configuration Manual

Figure 8-92. Using the show ip dhcp server statistics Command
Force10 #show ip dhcp server statistics
Automatic Bindings............................. 0
Expired Bindings............................... 0
Malformed Bindings............................. 0
Messages
----------
DHCP DISCOVER.................................. 5
DHCP REQUEST................................... 0
DHCP DECLINE................................... 0
DHCP RELEASE................................... 0
DHCP INFORM.................................... 0
Messages
----------
DHCP OFFER..................................... 0
DHCP ACK....................................... 0
DHCP NACK...................................... 0

Using the Switch as a BootP/DHCP Relay Agent

The S-Series also can serve as a BootP/DHCP relay agent, forwarding DHCP packets between clients and
a DHCP server (you can only use the switch as a relay agent to one DHCP server). This section describes
the concepts and tasks needed to configure the DHCP relay agent.

DHCP Relay Agent Overview

When the switch is configured to act as a DHCP relay agent, it forwards DHCP client broadcasted requests
to a DHCP server on another broadcast domain (Layer 3 network). These broadcasted requests from a
DHCP client use a destination IP address of 255.255.255.255 (all networks broadcast address).
The DHCP relay agent process is as follows:
1. The DHCP relay agent makes these two changes to the in-bound DHCP packet:
2. The relay agent forwards the rewritten DHCP request on behalf of a DHCP client to the DHCP server.
3. The DHCP server unicasts a reply to the DHCP relay agent, using the Gateway IP address field to
determine the subnet from which the DHCPDISCOVER, DHCPREQUEST, or DHCPINFORM
message originated.
4. The relay agent forwards the packet to the DHCP client.
132 | DHCP
a
The relay agent appends its own IP address to the source IP address of the DHCP frames
going to the DHCP server.
b The relay agent populates the Gateway IP address field with the IP address of the interface
on which the DHCP message is received from the client.
Received
----------
Sent
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