[CentOS] Yum Skipping filter question

Hi, all :

When I  run "yum update" command in my laptop , it displayed this :

root at foo Desktop]# yum update
Loaded plugins: aliases, changelog, fastestmirror, filter-data, keys, kmod,
list-data, priorities, protect-
              : packages, protectbase, security, tmprepo, verify
Loading mirror speeds from cached hostfile
 * addons: mirrors.163.com
 * base: mirrors.163.com
 * extras: mirrors.163.com
 * rpmforge: ftp-stud.fht-esslingen.de
 * updates: mirrors.163.com
Skipping filters plugin, no data
0 packages excluded due to repository protections
Skipping security plugin, no data
Setting up Update Process
No Packages marked for Update


I  searched on the Internet some time , but had not any useful answer .

Could someone help me ?

Thanks  in advance ~
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