DHCP Option 82, also known as the “DHCP Relay Agent Information” option, plays a crucial role in managed network environments, including those with wireless access points. Its primary purpose is to enhance the management and control of network resources by providing additional information about DHCP clients to the DHCP server. This additional information helps in making more informed and dynamic allocation decisions for IP addressing and policies. Here’s a detailed breakdown of its functionalities and benefits in the context of a wireless access point:
How It Works #
- When a DHCP client, such as a device connected to a wireless access point, requests an IP address, the request is intercepted by a DHCP relay agent or the access point itself if it’s acting in that capacity.
- Before forwarding the request to the DHCP server, the relay agent adds a “DHCP Option 82” field to the request. This field can contain various sub-options, such as the Circuit ID (identifying the port or access point the client is connected to) and the Remote ID (identifying the relay agent).
- Upon receiving the request, the DHCP server can examine this additional information to apply specific IP addressing rules, assign the client to a particular VLAN, or apply other network policies based on the client’s location or the access point it’s connected to.
- The DHCP server includes the Option 82 information in its response back to the relay agent, which uses it to deliver the server’s reply to the correct client.
Benefits in a Wireless Environment #
- Enhanced Security: By identifying the specific access point a request comes from, networks can prevent unauthorized access or assign different access levels based on the location or type of the device.
- Network Segmentation: Option 82 helps in implementing VLAN assignments dynamically, allowing devices connected to different wireless access points to be placed in appropriate VLANs without manual configuration.
- Efficient IP Address Management: It enables the DHCP server to make more informed decisions on IP address allocation, potentially saving IP address space and ensuring that IP configurations are optimized for the network’s topology.
- Troubleshooting and Management: The additional information provided can assist in network troubleshooting, monitoring, and management, offering insights into where devices are connecting in a large or complex environment.
In summary, DHCP Option 82 enriches DHCP transactions with crucial network topology information, facilitating advanced management, security, and allocation strategies in networks utilizing wireless access points. This capability is especially valuable in enterprise-level networks, where understanding the physical and logical placement of devices is critical for security, compliance, and efficient network operation.
Cambium DHCP Option 82 Configuration – using CNMaestro
Select WiFi AP Groups -> the profile you want to manage -> Configuration
Select Network
Scroll down to VLANs and edit the appropriate VLAN
In the pop-up window apply the DHCP Server configurations you want. Enter the DHCP Relay server and the options to be passed onto the clients.
Click Save, apply and all APs in that group will receive the updated Option 82 configuration.