DCHPRelay Agent
- Why need Relay Agent?
- Clients need DHCP server’s configuration info;
- Commonly Clients don’t reside in the subnet of Server;
- AP don’t forward broadcast packet by default;
- Solutions:
- Put DHCP servers in every subnet;
- Configure the AP to forward DHCP broadcast packet;
- Configure a DHCP relay agent in the network;
DHCP Relay Agent Information (Option 82)
- DHCP Relay Agent is used for passing messages between DHCP client and server.
- Relay Agent Information Option (Option 82) is an option inserted and removed by DHCP relay agent.
- The option is used for DHCP server to provide different services to DHCP clients.
Relay Agent Information Option 82
- We have to enable Relay Agent firstly, Relay Agent info Option (Opt-82) on our AP will take effect then.
- In some situation, we have two modes for Option 82:
- 1. Relay enabled, Option 82 enabled;
- 2. Relay disabled, Option 82 enabled;
Specifically the option works by setting two sub-options: Circuit ID and Remote ID. Those two are supposed to identify the remote device and the port where the DHCP request was received.
Configration
On our cnPilot E-series, we can enable DHCP Option82 with and without relay agent enabled.
1. Enable DHCP option82 with relay agent configuration
GUI
CLI
2. Enable DHCP option82 without relay agent configuration
GUI
CLI
When option 82 enabled in vlan interface with DHCP relay agent configured
When option 82 enabled in WLAN profile without DHCP relay agent configured
