Dell N3200-ON Networking N-Series Switches User Guide version 6.8.0 - Page 1189

The administrator globally enables DHCP relay and configures DHCP relay on the end-user ports of each switch as follows: console(config)#dhcp l2relay console(config)#interface range gi1/0/1-24 console(config-if)#dhcp l2relay console(config-if)#exit Then, the administrator configures the remote-id and circuit-id: console(config)#dhcp l2relay circuit-id vlan 10,20 console(config)#dhcp l2relay remote-id "Switch A" vlan 10,20 Finally, the administrator configures the uplink for DHCP relay and sets the interface to trust Option 82 information received on the interface: console(config)#dhcp l2relay console(config)#interface te1/0/1 console(config-if)#dhcp l2relay console(config-if)#dhcp l2relay trust console(config-if)#exit The administrator is using a Microsoft DHCP server. Microsoft DHCP servers do not have native support for DHCP Option 82, but it can be added using the DhcpServerCalloutEntry API to retrieve the information via the DhcpHandleOptionsHook configured on the switches. Adding Option 82 support enables choosing whether or not a particular DHCP server should respond to the DHCP request, and whether it should only respond to requests from a particular switch (as identified by the remote-id) and port (as identified by the circuit-id). For further information and an example, follow this web link: http://blogs.technet.com/b/teamdhcp/archive/2009/07/06/dhcp-server-calloutapi-usage.aspx For Linux-based systems, which natively support option 82, a configuration to serve two private pools (Pool1 and Pool2) and one public pool of DHCP addresses based upon the remote-id and circuit-id might look like the following: dhcpd.conf file: class "Pool1" { match option agent.remote-id; match option agent.circuit-id; } Layer-2 and Layer-3 Relay Features 1189