
Dynamic Host Configuration Protocol (DHCP) Introduction
©2008 Allied Telesis Inc. All rights reserved.
52.6
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
Software Version 5.2.1
You can define more than one relay destination on your device. The following table describes
how the relay agent forwards the packets.
To delete a relay destination, use the command:
awplus(dhcp-config)#
no ip dhcp-relay server-address <ip-addr>
When the ‘hops’ field in a BOOTP message exceeds a predefined threshold the BOOTP
message is discarded. The default of the threshold is 10. To set the threshold, use the
command:
awplus(config-if)#
ip dhcp-relay maxhops <1-255>
To display the current configuration of the DHCP relay agent, use the command:
awplus#
show ip dhcp-relay [interface <interface-name>]
DHCP Option 82 Relay
DHCP and BOOTP functionality includes the addition, removal and monitoring of DHCP
Option 82. Option 82 is also called the Relay Agent Information option.
DHCP relay agent can insert option 82 into the DHCP options field when forwarding client-
originated BOOTP/DHCP packets to a DHCP server. DHCP servers that are configured to
recognize option 82 may use the information to implement IP addresses, or other parameter
assignment policies, based on the network location of the client device.
For more information about option 82, see RFC 3046.
Option 82 can be:
■
added to packets relayed from the DHCP client to DHCP server
■
removed from packets relayed from DHCP server to DHCP client
■
checked from sources closer to the client
To enable the relay agent to insert its details into the option 82 field in requests received from
clients attached to a particular interface, use the command:
awplus(config)#
interface <
interface-name
>
awplus(config-if)#
ip dhcp-relay agent-option
This applies to requests received with no other agent relay information in the option 82 field.
Each device between a DHCP client and a DHCP server must act as a DHCP relay agent for a
request to reach the DHCP server. If a relay agent is not the first hop for a client, then it may
receive requests where another relay agent has filled the option 82 field. You can change how
the relay agent responds to these client requests, for example, you can set the relay agent to
forward the request with its own details in the option 82 field. To alter how the relay agent
responds to these requests, use the command:
If an interface has...
Then the relay agent relays BOOTP packets it
receives on that interface to...
one relay destination defined
the relay destination.
multiple relay destinations defined
each defined relay destination.
awplus(dhcp-config)#
ip dhcp-relay information policy [append|drop|keep|replace]