Ubigate iBG2016 Configuration Guide/Ed.00© SAMSUNG Electronics Co., Ltd. 93Using DHCP Relay with NATWhen NAT is enabled, the DHCP server may discard packets because thegiaddr does not match the source of the packet. Additionally, it may not knowhow to route the packet back to the client. See Figure 11.4. The solution is thatthe gateway address(giaddr) field needs to have IP address 192.168.20.1(in this example). The DHCP server configuration should be able to give10.1.1.x addresses for packets from 192.168.20.1. However, there may be alimitation that the DHCP server does not allow configuration using IPaddresses from a different subnet, although this is mentioned in the RFC.Figure 2.4 Typical Scenario for DHCP Relay with NATCommand Line InterfaceThe following are examples of command strings relevant to DHCP relayRouter# configure terminalRouter/configure# interface ethernet 0/0Router/configure/interface/ethernet(0/0)# dhcp_relayserver_address 20.1.1.1Disabling DHCP RelayRouter/configure/interface/ethernet(0/0)# no dhcp_relayserver_address 20.1.1.1Configuring the Gateway Address field when NAT is enabledRouter/configure/interface/ethernet(0/0)# dhcp_relaygateway_address 192.168.20.1DHCP ServerDHCP ClientDHCP ClientDHCP ClientRouter192.168.20.110.1.1.1PRIVATE PUBLICDHCP Pelay AgentNetwork Address Translation10.1.1.1 xNetwork
