Black Box LR11xx Series Router Configurations Guide
Figure 2 BOOTP Requests
Broadcast BOOTREQUEST |
| Unicast BOOTREQUEST |
DHCP Client | DHCP Relay Agent | DHCP Server |
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
Unicast/Broadcast
BOOTREPLY
Unicast
BOOTREPLY
DHCP Client | DHCP Relay Agent | DHCP Server |
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
DHCP Client
10.1.1.x Network
DHCP Client
DHCP Client
Network Address Translation
PRIVATE | PUBLIC |
192.168.20.1 | |
10.1.1.1 |
|
| Router |
DHCP Relay Agent | DHCP Server |
1.1.4 Command Line Interface
The following are examples of command strings relevant to DHCP relay:
1.1.4.1 Enabling DHCP Relay
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