Are you saying that you want to assign the service port a public ip address and place that in the DMZ so you can access the WLC remotely? I guess you can do that, but I wouldn't. You could always vpn or do a nat translation to the management ip if you really wanted to. The key here is to make sure that your management ip and service port ip can't communicate or else it will cause you some issues. If you do this, then you should crate an acl blocking traffic from the management ip to the service port ip.
-Scott
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