--> Light Weight Access Point discovers Wireless Lan Controller by using two methods
i) Manually Configuring IP address of WLC on AP.
ii) Dynamically discovering WLC IP Address ( It can be done by 3 methods).
1) Broadcast
--> As soon as Light Weight Access Point gets the IP address from DHCP Server, it sends broadcast on local subnet.
--> If you want to forward this broadcasts to the subnet where WLC is configured, we need to configure IP helper command.
--> We need to give two commands on the Router or MLS which is acting as DHCP Relay Agent.
Router(config)# int fa0/0
Router (config-if)# ip helper-address 192.168.1.1
Router(config)# ip forward-protocol udp 5246
2) DHCP option 43 and option 60
--> If we have DHCP Server in the network then we can use option 43 which tells the IP address of Wireless Controller to Access Point.
--> Option 43 is not specific to Access Point Model, whereas Option 60 is specific to Access Point Model.
3) DNS
--> Once Light Weight Access Point gets IP Address, it tries to resolve CISCO-CAPWAP-CONTROLLER.localdomain to get WLC IP Address.
--> CISCO-CAPWAP-CONTROLLER.localdomain A host need to be configured in DNS server pointing towards to WLC IP Address.
Joining Process
--> Once LAP discovers the list of IP address of Wireless Lan Controllers, then it uses the following order to join WLC
i) Manually Configured Primary WLC on AP.
ii) Manually Configured Secondary WLC on AP.
iii) Manually Configured Tertiary WLC on AP
iv) WLC with Master Controller Flag set
v) Least Loaded Controller.
--> Then AP sends its own certificate to WLC and WLC sends its own certificate to AP for forming DTLS Tunnel.
--> Then AP sends Join request to WLC, WLC responds with Join response.
--> Once AP joins WLC, WLC checks the code version of AP.
--> If AP is running different code compared to WLC then AP downloads the same code which is running on WLC and reboots with new code.
--> If AP is running with the same code then WLC sends Configuration for AP.
Note : To check which WLC information AP is having, then we need to use following command on AP.
AP# show capwap client config
mwarName WLC1
mwarIPAddress 10.100.5.1
mwarName WLC2
mwarIPAddress 10.100.5.2
mwarName WLC3
mwarIPAddress 10.100.5.3
i) Manually Configuring IP address of WLC on AP.
ii) Dynamically discovering WLC IP Address ( It can be done by 3 methods).
1) Broadcast
--> As soon as Light Weight Access Point gets the IP address from DHCP Server, it sends broadcast on local subnet.
--> If you want to forward this broadcasts to the subnet where WLC is configured, we need to configure IP helper command.
--> We need to give two commands on the Router or MLS which is acting as DHCP Relay Agent.
Router(config)# int fa0/0
Router (config-if)# ip helper-address 192.168.1.1
Router(config)# ip forward-protocol udp 5246
2) DHCP option 43 and option 60
--> If we have DHCP Server in the network then we can use option 43 which tells the IP address of Wireless Controller to Access Point.
--> Option 43 is not specific to Access Point Model, whereas Option 60 is specific to Access Point Model.
3) DNS
--> Once Light Weight Access Point gets IP Address, it tries to resolve CISCO-CAPWAP-CONTROLLER.localdomain to get WLC IP Address.
--> CISCO-CAPWAP-CONTROLLER.localdomain A host need to be configured in DNS server pointing towards to WLC IP Address.
Joining Process
--> Once LAP discovers the list of IP address of Wireless Lan Controllers, then it uses the following order to join WLC
i) Manually Configured Primary WLC on AP.
ii) Manually Configured Secondary WLC on AP.
iii) Manually Configured Tertiary WLC on AP
iv) WLC with Master Controller Flag set
v) Least Loaded Controller.
--> Then AP sends its own certificate to WLC and WLC sends its own certificate to AP for forming DTLS Tunnel.
--> Then AP sends Join request to WLC, WLC responds with Join response.
--> Once AP joins WLC, WLC checks the code version of AP.
--> If AP is running different code compared to WLC then AP downloads the same code which is running on WLC and reboots with new code.
--> If AP is running with the same code then WLC sends Configuration for AP.
Note : To check which WLC information AP is having, then we need to use following command on AP.
AP# show capwap client config
mwarName WLC1
mwarIPAddress 10.100.5.1
mwarName WLC2
mwarIPAddress 10.100.5.2
mwarName WLC3
mwarIPAddress 10.100.5.3
Pretty detailed guide on Wireless Lan Controllers, thanks!
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