Centos 6 expired on 30th November 2020 You have to edit the CentOS-Base.repo to point to vault every where or set up a proxy to change the search to the vault Index of /6.10 https://vault.centos.org/6.10/
in the repo file change everywhere
name=CentOS-6.10 - Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
baseurl=http://vault.centos.org/6.10/centosplus/$basearch/
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
depending on what you have in the file
grep 'name=' CentOS-Base.repo
name=CentOS-$releasever - Base
name=CentOS-$releasever - Updates
name=CentOS-$releasever - Addons
name=CentOS-$releasever - Extras
name=CentOS-$releasever - Plus
name=CentOS-$releasever - Contrib