Hi,

  to authenticate with the eduroam user. It seems that although the
  request is proxied, my server tries to locally check the authorized
  attributes of the user against my local ldap server. And since no
  such user exists ldap returns : object not found

use unlang to put a protection wrapper around your ldap eg

if (%{realm} == /yourrealm.com/){
ldap
}

I solved it in the users file:

DEFAULT Realm == "yourrealm.com", Ldap-Group == "your_ldap_group"
                        Service-Type = "Framed-User",
                        Reply-Message = "Eduroam instuition",
                        Framed-MTU = 1300,
                        Tunnel-Type = VLAN,
                        Tunnel-Medium-Type = IEEE-802,
                        Tunnel-Private-Group-Id = "xxxx"