Código:
[root@dos ~]# cat /etc/yum.repos.d/CentOS-Base.repo
[base]
name=CentOS-$releasever - Base
baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/os/$basearch
gpgcheck=1
#released updates
[update]
name=CentOS-$releasever - Updates
baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/updates/$basearch
gpgcheck=1
#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=http://mirror.centos.org/centos/$releasever/addons/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/addons/$basearch
gpgcheck=1
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/extras/$basearch
gpgcheck=1
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/centosplus/$basearch
gpgcheck=1
enabled=1
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/contrib/$basearch
gpgcheck=1
enabled=1
#packages in testing
[testing]
name=CentOS-$releasever - Testing
baseurl=http://mirror.centos.org/centos/$releasever/testing/$basearch/
ftp://ftp.inf.utfsm.cl/pub/Linux/centos/$releasever/testing/$basearch
gpgcheck=1
enabled=0
[root@dos ~]#
Así quedó después de la instalación y funciona OK; sólo le agregué un mirror más cercano. No entiendo por qué tienes problemas. ¿Tal vez estás detrás de un proxy?