Owner's Manual

628 | Chapter 20. IPv4 Unicast Routing
NETGEAR 8800 User Manual
taken depends on the configured policy (drop packet, keep existing option 82 value, or
replace the existing option). If the incoming DHCP request is tagged, then that VLAN ID is
added to the circuit ID sub option of option 82; otherwise, the default VLAN ID is added.
• DHCP Reply: When the option 82 information check is enabled, the packets received
from the DHCP server are checked for option 82 information. If the remote ID sub-option
is the switch's MAC address, the packet is sent to the client; if not, the packet is dropped.
If the check is not enabled. the packets are forwarded as-is.
The DHCP relay agent option consists of two pieces of data, called sub-options. The first is
the agent circuit ID sub-option, and the second is the agent remote ID sub-option. When the
DHCP relay agent option is enabled on switches running XCM8800, the value of these
sub-options is set as follows:
• Agent circuit ID sub-option: The full circuit ID string uses the format
<vlan_info>-<port_info>. You can use the default values for vlan_info and port_info, or
you can configure these values as described later in this section.
• Agent remote ID sub-option: Always contains the Ethernet MAC address of the relaying
switch. You can display the Ethernet MAC address of the switch by issuing the
show
switch command.
Note: For more general information about the DHCP relay agent
information option, see RFC 3046.
The following sections describe how to manage this feature:
• Enabling and Disabling the DHCP Relay Agent Option on page 628
• Enabling and Disabling DHCP Packet Checking on page 628
• Configuring the DHCP Packet Handling Policy on page 629
• Configuring the DHCP Agent Circuit ID Suboption on page 629
Enabling and Disabling the DHCP Relay Agent Option
To enable the DHCP relay agent option, use the following command after configuring the
DHCP/BOOTP relay function:
configure bootprelay dhcp-agent information option
To disable the DHCP relay agent option, use the following command:
unconfigure bootprelay dhcp-agent information option
Enabling and Disabling DHCP Packet Checking
In some instances, a DHCP server may not properly handle a DHCP request packet
containing a relay agent option. To prevent DHCP reply packets with invalid or missing relay
agent options from being forwarded to the client, use the following command:
configure bootprelay dhcp-agent information check