DHCP option 43 is a vendor-specific option that supplies lightweight access points (LWAPs) with the IP address of their wireless LAN controller (WLC). Because LWAP addresses are usually leased dynamically, the DHCP server can provide the controller address during management-VLAN address assignment. section 21.1.1
On a multilayer switch acting as the DHCP server, configure option 43 in the management pool used by LWAPs. Option 42 is separate: it supplies an NTP server address, whereas option 43 identifies the WLC. section 21.1.1
Providing the WLC address
For a management network using 192.168.1.0/24, the DHCP pool can provide the switch as the default gateway and 192.168.1.100 as the WLC: `ip dhcp pool Management`, `network 192.168.1.0 255.255.255.0`, `default-router 192.168.1.1`, and `option 43 ip 192.168.1.100`. section 21.1.1
SW1(config)# ntp master #1 SW1(config)# ip dhcp pool Management #2 SW1(dhcp-config)# network 192.168.1.0 255.255.255.0 #2 SW1(dhcp-config)# default-router 192.168.1.1 #3 SW1(dhcp-config)# option 42 ip 192.168.1.1 #4 SW1(dhcp-config)# option 43 ip 192.168.1.100 #5 SW1(dhcp-config)# ip dhcp pool Internal #6 SW1(dhcp-config)# network 10.0.0.0 255.255.255.0 #6 SW1(dhcp-config)# default-router 10.0.0.1 #6 SW1(dhcp-config)# option 42 ip 10.0.0.1 #6 SW1(dhcp-config)# ip dhcp pool Guest #7 SW1(dhcp-config)# network 10.1.0.0 255.255.255.0 #7 SW1(dhcp-config)# default-router 10.1.0.1 #7 SW1(dhcp-config)# option 42 ip 10.1.0.1 #7 #1 Makes SW1 an NTP server #2 Creates a pool for the Management VLAN and assigns its IP range #3 Specifies SW1 as the default gateway #4 Tells DHCP clients to use SW1 as their NTP server #5 Tells DHCP clients (AP1) to use WLC1 as their WLC #6 Configures a pool for the Internal WLAN/VLAN #7 Configures a pool for the Guest WLAN/VLAN
Browse the complete DHCP configuration showing the management, internal, and guest pools and the placement of option 43. section 21.1.1
