Samsung Ubigate iBG3026, Configuration Manual

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Ubigate iBG3026 Configuration Guide/Ed.00
© SAMSUNG Electronics Co., Ltd.
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Using DHCP Relay with NAT
When NAT is enabled, the DHCP server may discard packets because the
giaddr does not match the source of the packet. Additionally, it may not know
how to route the packet back to the client. See Figure 11.4. The solution is that
the gateway address(giaddr) field needs to have IP address 192.168.20.1(in
this example). The DHCP server configuration should be able to give 10.1.1.x
addresses for packets from 192.168.20.1. However, there may be a limitation
that the DHCP server does not allow configuration using IP addresses from a
different subnet, although this is mentioned in the RFC.
Figure 11.4 Typical Scenario for DHCP Relay with NAT
Command Line Interface
The following are examples of command strings relevant to DHCP relay
Router# configure terminal
Router/configure# interface ethernet 0/0
Router/configure/interface/ethernet(0/0)# dhcp_relay
server_address 20.1.1.1
Disabling DHCP Relay
Router/configure/interface/ethernet(0/0)# no dhcp_relay
server_address 20.1.1.1
Configuring the Gateway Address field when NAT is enabled
Router/configure/interface/ethernet(0/0)# dhcp_relay
gateway_address 192.168.20.1
DHCP Server
DHCP Client
DHCP Client
DHCP Client
Router
192.168.20.1
10.1.1.1
PRIVATE PUBLIC
DHCP Pelay Agent
Network Address Translation
10.1.1.1 x
Network