HP 6120XG HP ProCurve Series 6120 Blade Switches Multicast and Routing Guide - Page 95
Option 82 Server Support, Example of a DHCP Option 82 Application
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Note IP Routing Features Configuring DHCP Relay The routing switch's DHCP Relay Information (Option 82) feature can be used in networks where the DHCP server(s) are compliant with RFC 3046 Option 82 operation. DHCP Servers that are not compliant with Option 82 operation ignore Option 82 fields. For information on configuring an Option 82 DHCP server, refer to the documentation provided with the server application. Some client applications can append an Option 82 field to their DHCP requests. Refer to the documentation provided for your client application. It is not necessary for all relay agents on the path between a DHCP client and the server to support Option 82, and a relay agent without Option 82 should forward DHCP packets regardless of whether they include Option 82 fields. However, Option 82 relay agents should be positioned at the DHCP policy boundaries in a network to provide maximum support and security for the IP addressing policies configured in the server. Option 82 Server Support To apply DHCP Option 82, the routing switch must operate in conjunction with a server that supports Option 82. (DHCP servers that do not support Option 82 typically ignore Option 82 fields.) Also, the routing switch applies Option 82 functionality only to client request packets being routed to a DHCP server. DHCP relay with Option 82 does not apply to switched (non-routed) client requests. For information on configuring policies on a server running DHCP Option 82, refer to the documentation provided for that application. Relay Agent "1" (Routing Switch) with DHCP Option 82 Enabled VLAN VLAN 10 20 10.10.10.1 10.10.20.1 Switch "A" 10.10.10.2 Switch "B" 10.10.20.3 Client Client Client 1 2 3 Client Client Client 4 5 6 Policy Boundaries Figure 3-21. Example of a DHCP Option 82 Application 10.10.30.1 10.10.20.2 DHCP Option 82 Server Relay Agent "2" (Routing Switch) without DHCP Option 82 Enabled 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. 3-49