Introduction- The DHCP Information option (Option 82) is commonly used in metro or large enterprise deployments to provide additional information on “physical attachment” of the client. Option 82 is supposed to be used in distributed DHCP server/relay environment, where relays insert additional information to identify the client’s point of attachment.
Feature Notes- DHCP relay is supposed to insert the “giaddr” field in the relayed DHCP packets, so that DHCP server may identify the pool to be used for the request. The choice of the pool is made based on the “giaddr” field or the incoming interface, if the “giaddr” is missing or zero . Option 82 serves as refinement to the request, allowing the DHCP server to select a “sub-range” in the pool.
The controller, when acting as a DHCP relay agent, inserts information about the AP and SSID through which a client is connecting into the DHCP request.
The MAC address is the hardware address and ESSID is an alphanumeric name that uniquely identifies a wireless network. For configuring Option-82, select the VLAN interface mapped for the VAP profile and do the following configurations.
Network Topology- DHCP Server -->Gateway--> Controller (DHCP Relay Agent) --> AP --> Client
- Navigate to Configuration > Network > IP >IP Interfaces.
- Click Edit next to the VLAN ID for which you want to configure Option 82.
- Under DHCP Helper Address select Mac or Mac Essid from the Option-82 drop-down menu.
- Click Apply
This example enables Option 82 for VLAN 5 using ESSID. You can include only the MAC address or MAC address and ESSID.
(host) (config) #interface vlan 5
(host) (config-subif)#option-82 mac essid
Troubleshooting- Enable Debugging for network
logging level debugging network subcat dhcp