Hi,
Yes its normal. If you want you can block it by creating ACL on WLC.
http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/81733-contr-acls-rle.html
http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wlan-security/71978-acl-wlc.html
Regards
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