In my environment, Active Directory is a sprawling mess of nested directory after nested directory. Security groups are created in nested folders for a division leading to a single LDAP filter line >150 characters. Tying two or more LDAP filters together results in a filter hundreds of characters long.

| Started PUT "/auth_source_ldaps/5-Active%20Directory" for 139.126.210.241 at 2016-02-17 13:32:21 -0600
2016-02-17 13:32:21 [app] [I] Processing by AuthSourceLdapsController#update as */*
2016-02-17 13:32:21 [app] [I] Parameters: {"utf8"=>"✓", "authenticity_token"=>"[FILTERED]", "auth_source_ldap"=>{"name"=>"Active Directory", "host"=>"[FILTERED]", "tls"=>"1", "port"=>"636", "server_type"=>"active_directory", "account"=>"[FILTERED]", "account_password"=>"[FILTERED]", "base_dn"=>"[FILTERED]", "groups_base"=>"", "ldap_filter"=>"(|(memberOf=CN=<SOME_LONG_MESS_OF_CHARACTERS_GREATER_THAN_150_CHARACTERS>)(memberOf=CN=<SOME_OTHER_HUGE_FILTER_STRING_GREATER_THAN_150_CHARACTERS>))", "onthefly_register"=>"0", "usergroup_sync"=>"0", "attr_login"=>"sAMAccountName", "attr_firstname"=>"", "attr_lastname"=>"", "attr_mail"=>"", "attr_photo"=>""}, "id"=>"5-Active Directory"}
2016-02-17 13:32:21 [app] [I] Failed to save: Ldap filter is too long (maximum is 255 characters)
2016-02-17 13:32:21 [app] [I] Rendered auth_source_ldaps/_form.html.erb (19.3ms)
2016-02-17 13:32:21 [app] [I] Rendered auth_source_ldaps/edit.html.erb (21.1ms)
2016-02-17 13:32:21 [app] [I] Completed 200 OK in 50ms (Views: 26.0ms | ActiveRecord: 1.1ms)