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As can be seen by the examples, none of these contains the crucial @-sign , and thus none should not be sent upstream to the national proxies. Permitting your users to connect to eduroam on campus or at their student accommodation handled by your own RADIUS servers using a non-realm username will only lead to a bad user experience when your users doing so attempt to roam off-site (like at other institutions in your location or even abroad) because the realm-less username cannot be routed by those other institutions.
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