Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1694)

Dynamic Host Configuration Protocol (DHCP) Introduction
Software Reference for x310 Series Switches
63.8 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
To delete a DHCP relay destination, use the command:
See the ip dhcp-relay server-address command on page 64.18 and the service dhcp-
relay command on page 64.21 for command description and command examples. DHCP
servers with IPv4 and IPv6 addresses are configured with ip dhcp-relay server-address .
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:
To display the current configuration of the DHCP relay agent, use the command:
DHCP Relay Agent Information Option (Option 82)
You can use DHCP Relay Agent Information Option (Option 82) to protect your switch
from spoofing attacks, where untrusted hosts can send requests for IP addresses to access
the network. The switch relays these requests to DHCP servers and the servers send IP
address leases in response. Untrusted hosts could then use these IP addresses for spoofing
attacks. Option 82 contains information about the location of a DHCP client for the DHCP
server.
Enabling the DCHP Relay Agent Information Option feature on the switch allows the
switch to insert extra information into the DHCP packets that it is relaying. This
information enables accurate identification of a subscriber, as it states which interface on
which relay switch the subscriber is connected to. The information is stored in an optional
field in the DHCP packet header, the relay agent-information option field, with the option
ID 82.
The DHCP relay agent inserts the Option 82 information into the DHCP packets that it is
relaying 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. Alternatively, the server can simply log
this information to create a detailed audit trail of the locations of the clients to which
given addresses were allocated at given times.
awplus(config-if)# no ip dhcp-relay server-address {address>| }
awplus(config-if)# ip dhcp-relay maxhops <1-255>
awplus# show ip dhcp-relay [interface ]