HI,
Check this documents, it may helps:
Guest WLAN and Internal WLAN using WLCs Configuration Example
http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-vlan/70937-guest-internal-wlan.html
you can put up another SSID for the guests, and you can connect the DSL connection direclty to the WLC on another port. You just need to create an interface with an appropriate IP address for the DSL connection.
Regards
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