Extreme Networks ExtremeWare 7.2e, Installation And User Manual

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228 ExtremeWare 7.2e Installation and User Guide
IP Unicast Routing
packet that is to be relayed by the switch. Similarly, if a DHCP reply received by the switch contains a
valid relay agent option, the option will be stripped from the packet before it is relayed to the client.
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 ExtremeWare, the value of these sub-options is set as follows:
• Agent circuit ID sub-option
: Contains the ID of the port on which the original DHCP request packet
was received. This ID is encoded as (port_number). For example, if the DHCP request were received
on port 12, the agent circuit ID value would be 3012. On non-slot-based switches, the agent circuit ID
value is simply the port number.
• 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.
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
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
To disable checking of DHCP replies, use this command:
unconfigure bootprelay dhcp-agent information check
A DHCP relay agent may receive a client DHCP packet that has been forwarded from another relay
agent. If this relayed packet already contains a relay agent option, then the switch will handle this
packet according to the configured DHCP relay agent option policy. To configure this policy, use the
following command:
configure bootprelay dhcp-agent information policy <policy>
where
<policy>
must be one of the following values:
replace
,
keep
, or
drop
. The default relay policy
is
replace
. To configure the policy to the default, use this command:
unconfigure bootprelay dhcp-agent information policy
For more general information about the DHCP relay agent information option, refer to RFC 3046.
Verifying the DHCP/BOOTP Relay Configuration
To verify the DHCP/BOOTP relay configuration, use the following command:
show ipconfig
This command displays the configuration of the BOOTP relay service, and the addresses that are
currently configured.