Black Box LR1102A-T1/E1 - Manual (Page 12)

Black Box LR11xx Series Router Configurations Guide
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Figure 2 BOOTP Requests
1.1.2.2 BOOTP Replies
BOOTP replies are messages from the server to the client. Reply messages include DHCP OFFER, DHCP ACK, DHCP
NAK, etc. The relay agent looks up the MAC address and either sends the packet to the client or broadcasts it on the
LAN.
Figure 3 BOOTP Replies
1.1.3 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 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 4 A Typical Scenario
1.1.4 Command Line Interface
The following are examples of command strings relevant to DHCP relay:
1.1.4.1 Enabling DHCP Relay
Broadcast BOOTREQUEST Unicast BOOTREQUEST
Tasman 1400
DHCP Relay Agent DHCP Client DHCP Server
Unicast/Broadcast Unicast
Tasman 1400
DHCP Relay Agent DHCP Client DHCP Server
BOOTREPLY BOOTREPLY
Tasman 1400
DHCP Relay Agent
DHCP Client
DHCP Server DHCP Client
DHCP Client
Router
PRIVATE PUBLIC
192.168.20.1
10.1.1.1 10.1.1.x
Network
Network Address Translation