DHCP with WLC

DHCP in WLC are of two types : Internal and External DHCP

Internal DHCP : DHCP server can be created in WLC.

Packet Flow

1. Client send DHCP discover on all subnet as broadcast
2. WLC forward the DHCP discover via DHCP proxy to internal DHCP server ip address(Management interface IP of WLC)
3. Internal DHCP server send DHCP offer to WLC proxy agent.
4. WLC send unicast DHCP offer to client with source address of WLC management Interface IP.
5. Client send DHCP request to WLC on management interface IP.
6. WLC send unicast DHCP request to internal server via DHCP proxy
7. Internal DHCP server sends DHCP ACK to DHCP proxy.
8. WLC send unicast DHCP ACK to client

External DHCP - (Proxy and Bridge)

• Proxy – WLC becomes the proxy for DHCP messages.

Packet Flow

1. Client boots up and send DHCP Discover on all subnet broadcast.
2. WLC unicast this packet to DHCP server(as configured on WLC interface)
3. DHCP server send DHCP offer to WLC.
4. WLC unicast DHCP offer to Client with source address as WLC virtual IP address.
5. Client send DHCP request to WLC on Virtual address because Client think that this virtual IP is DHCP server address
6. WLC unicast DHCP request to DHCP server which returned the first offer to the client.
7. DHCP server send ACK to WLC
8. WLC unicast ACK from virtual IP to the client.

• Bridging – DHCP messages are exchanged directly with client and DHCP Server.

Packet Flow

1. Client send DHCP Discover on all subnet broadcast which is bridged by controller
2. DHCP server send DHCP offer to Client
3. Client send DHCP request to all subnet
4. DHCP server send ACK to client in unicast packet