Symptom
In 16.12 CLI you can configure the NAT only following way:
WLC16(config)#wireless management interface Vlan39 nat public-ip X.X.X.X
This looks following way in configuration:
wireless management interface Vlan39
wireless management interface Vlan39 nat
wireless management interface Vlan39 nat public-ip X.X.X.X
On the 17.5.1 the things are different:
WLC(config)#wireless management interface Vlan39 n?
% Unrecognized command
The config is done in the following way:
WLC(config)#wireless management interface Vlan39
WLC(config-mgmt-interface)#public-ip X.X.X.X
The command does not exist on 17.5.1.
This the issue when upgrading from 16.12 to 17.5.1, as the does not exist anymore.
This means that the WLC will disregard this command when booting.
If the APs are joined using NAT interface IP, the APs will drop from WLC and will not be able to join until the configuration is corrected.
Instead you need you use the following:
wireless management interface INTERFACE
public-ip PUBLIC_IP
Conditions
9800 Upgrade from 16.12.x to 17.x.x release
Workaround
If using NAT interface on WLC, manually configure the NAT:
wireless management interface INTERFACE
public-ip PUBLIC_IP
