Product guide

IP Routing Features
Configuring DHCP Relay
replace: Configures the switch to replace existing Option
82 field(s) in an inbound client DHCP packet with
an Option 82 field for the switch.
The replacement Option 82 field includes the switch
circuit ID (inbound port number*) associated with
the client DHCP packet, and the switch remote ID.
The default switch remote ID is the MAC address of
the switch on which the packet was received from the
client. To use the incoming VLAN’s IP address or the
Management VLAN IP address (if configured) for the
remote ID instead of the switch MAC address, use the
ip or mgmt-vlan option (below).
drop: Configures the routing switch to unconditionally
drop any client DHCP packet received with existing
Option 82 field(s). This means that such packets will
not be forwarded. Use this option where access to the
routing switch by untrusted clients is possible.
If the routing switch receives a client DHCP packet
without an Option 82 field, it adds an Option 82 field
to the client and forwards the packet. The added
Option 82 field includes the switch circuit ID
(inbound port number*) associated with the client
DHCP packet, and the switch remote ID. The default
switch remote ID is the MAC address of the switch
on which the packet was received from the client. To
use the incoming VLAN’s IP address or the Manage-
ment VLAN IP address (if configured) for the remote
ID instead of the switch MAC address, use the ip or
mgmt-vlan option (below).
keep: For any client DHCP packet received with existing
Option 82 field(s), configures the routing switch to
forward the packet as-is, without replacing or
adding to the existing Option 82 field(s).
[validate]: This option operates when the routing switch
is configured with append, replace, or drop as a
forwarding policy. With validate enabled, the
routing switch applies stricter rules to an incoming
Option 82 server response to determine whether to
forward or drop the response. For more information,
refer to “Validation of Server Response Packets” on
page 5-129.
5-132