Siemens S323 User Manual

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User Manual                                                                               UMN:CLI 
SURPASS hiD 6615 S223/S323 R1.5 
A50010-Y3-C150-2-7619                                                                         251 
Before configuring DHCP server or relay, you need to use the service dhcp command 
first to activate the DHCP function in the system. 
 
8.8.4.1 Packet 
Forwarding 
Address 
A DHCP client sends DHCP_DISCOVER message to a DHCP server. DHCP_DISCOVER 
message is broadcasted within the network to which it is attached. If the client is on a 
network that does not have any DHCP server, the broadcast is not forwarded because 
the switch is configured to not forward broadcast traffic. To solve this problem, you can 
configure the interface that is receiving the broadcasts to forward certain classes of 
broadcast to a helper address. 
To specify a packet forwarding address, use the following command. 
Command Mode 
Description 
ip dhcp helper-address
 A.B.C.D 
Specifies a packet forwarding address. More than one 
address is possible. 
A.B.C.D: DHCP server address 
no ip dhcp helper-address
 
{A.B.C.D | all
Interface 
Deletes a specified packet forwarding address. 
 
If a packet forwarding address is specified on an interface, the hiD 6615 S223/S323 will 
enable a DHCP relay agent. 
You can also specify an organizationally unique identifier (OUI) when configuring a packet 
forwarding address. The OUI is a 24-bit number assigned to a company or organization 
for use in various network hardware products which is a first 24 bits of a MAC address. If 
an OUI is specified, a DHCP relay agent will forward DHCP_DISCOVER message to a 
specific DHCP server according to a specified OUI. 
To specify a packet forwarding address with an OUI, use the following command. 
Command Mode 
Description 
ip dhcp oui
  XX:XX:XX  helper-
address
 A.B.C.D 
Specifies a packet forwarding address with an OUI. 
More than one address is possible. 
XX:XX:XX: OUI (first 24 bits of a MAC address in the 
form of hexadecimal) 
A.B.C.D: DHCP server address 
no ip dhcp oui
 XX:XX:XX 
[helper-address A.B.C.D
Interface 
Deletes a specified packet forwarding address. 
 
8.8.4.2 
Smart Relay Agent Forwarding 
Normally, a DHCP relay agent forwards DHCP_DISCOVER message to a DHCP server 
only with a primary IP address on an interface, even if there is more than one IP address 
on the interface. 
If the smart relay agent forwarding is enabled, a DHCP relay agent will retry sending 
DHCP_DISCOVER message with a secondary IP address, in case of no response from 
the DHCP server. 
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