Hello @Noovi,
The [ip dhcp relay information option server-id-override] command is used when the WLC is acting as a DHCP relay agent. When the WLC receives DHCP requests from wireless clients, it forwards them to the DHCP server. This command instructs the WLC to override the DHCP server's ID with its own ID when relaying the DHCP request. This can be useful in some scenarios where DHCP server identification needs to be modified during the relay process.
--When the WLC is acting as a DHCP relay agent, it receives DHCP requests from wireless clients and forwards them to the DHCP server. During this relay process, the DHCP relay agent (WLC) includes various DHCP relay options in the DHCP packets to provide additional information to the DHCP server. One of these options is the Server Identifier (Option 54) field, which indicates the IP address of the DHCP relay agent (WLC) to the DHCP server. By default, the WLC sets the Server Identifier field to its own IP address. However, with the ip dhcp relay information option server-id-override command, you can override this default behavior. When this command is enabled on the WLC, it replaces the default IP address in the Server Identifier field with the IP address specified in the next-hop address or interface IP address of the outgoing DHCP relay packet.
The use of this command can be relevant in specific scenarios where the DHCP server needs to identify the DHCP relay agent differently. For example, in networks with multiple WLCs acting as DHCP relay agents, each WLC can override the Server Identifier field with its own IP address to help the DHCP server distinguish between them.
The [ip dhcp server use subscriber-id client-id] command configures the WLC to use the client-id as the subscriber ID when acting as a DHCP server. The subscriber ID is a unique identifier used by the DHCP server to differentiate between clients. By using the client-id as the subscriber ID, the WLC can better manage and track DHCP leases for individual clients.
--When the WLC is configured to act as a DHCP server for wireless clients, it assigns IP addresses dynamically to these clients from a predefined pool (DHCP pool). To effectively manage DHCP leases and uniquely identify clients, DHCP servers use a Subscriber Identifier (Subscriber-ID). The Subscriber-ID is an optional field that can be used to distinguish clients based on specific characteristics.
With the ip dhcp server use subscriber-id client-id command, the WLC configures itself to use the DHCP client's Client Identifier (Client-ID) as the Subscriber Identifier when allocating IP addresses. The Client-ID is a unique identifier sent by the DHCP client in its DHCP request packet. By using the Client-ID as the Subscriber Identifier, the WLC can associate each DHCP lease with a specific client, even if the client has multiple interfaces or wireless devices associated with it.
Using the Client-ID as the Subscriber Identifier allows the WLC to maintain separate DHCP leases for different devices or interfaces of a single client, preventing IP address conflicts and improving DHCP lease management efficiency.
Sources:
https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/content/en/us/td/docs/ios-xml/ios/ipaddr_dhcp/configuration/xe-3s/dhcp-xe-3s-book/dhcp-relay-svr-option-82-xe.html.xml
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_dhcp/configuration/15-sy/dhcp-15-sy-book/dhcp_server_port-based_address_allocation.html
Best regards
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