IP Routing Features
Configuring DHCP Relay
For information on configuring policies on a server running DHCP Option 82,
refer to the documentation provided for that application.
Figure 5-62. Example of a DHCP Option 82 Application
Switch “A”
10.10.10.2
VLAN
10
10.10.10.1
Client
3
DHCP
Option
82
Server
Subnets 10 and 20 in relay agent “1”
form policy boundaries that can be
defined by the IP address of the subnet
on which the client request is received.
Relay Agent “1” (Routing Switch)
with DHCP Option 82 Enabled
Client
1
Client
2
VLAN
20
10.10.20.1
Switch “B”
10.10.20.3
Client
6
Client
4
Client
5
10.10.20.2
10.10.30.1
Relay Agent “2” (Routing
Switch) without DHCP
Option 82 Enabled
Policy Boundaries
Terminology
Circuit ID: In Option 82 applications, the number of the port through which
the routing switch receives a DHCP client request. On ProCurve fixed-port
switches, the Circuit ID of a given port corresponds to the port number
appearing on the front of the switch for that port. On ProCurve chassis
switches, the port number for a given port corresponds to the internal if Index
number for that port. This value is included as a suboption in an Option 82
field that the relay agent appends to a Client DHCP request before forwarding
the request toward a DHCP server. (For more on Circuit ID, refer to “Circuit
ID” in the list on page 5-139.)
DHCP Policy Boundary: For Option 82 applications, an area of a network
as defined by connection to a given routing switch or subnet and/or a specific
port belonging to the routing switch or subnet.
DHCP relay agent: See Relay Agent.
Forwarding Policy: The Option 82 method the routing switch uses to process
incoming client DHCP requests. For a given inbound DHCP client request, the
forwarding policy determines whether the routing switch will add Option 82
information, replace existing Option 82 information, or leave any existing
information unchanged. The policy also determines whether the routing
switch will forward the client request toward a DHCP server or drop the
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