[CentOS] CentOS 6 update issues

Hello all,

I manage a few servers overseas that are running CentOS 6.

When performing a yum update, it fails because it's trying to download from:

mirror.centos.org/centos/*6.6*/extras/x86_64/repodata/repomd.xml


Which fails due to the fact that the entire 6.6 directory is empty on all
of the mirrors I have checked. From what I can tell it should be using:

mirror.centos.org/centos/*6*/extras/x86_64/repodata/repomd.xml


Does anyone have any idea why this would be happening? Obviously changing
the CentOS-Base file to use 'baseurl' rather than 'mirrorlist' is a
workaround, but I would prefer a more permanent solution, and would like to
know why this is happening.

Thanks in advance.