Update of packages using default repositories (base, update etc.) is no longer applicable.You should switch boxes, run on CentOS 5.x., to so called Vault repositories.
1- Disable base, updates and other enabled repositories (where enabled=1 is set) in the CentOS-Base.repo:
sed -i 's/enabled=1/enabled=0/g' /etc/yum.repos.d/CentOS-Base.repo
create a new repo file and enter the following lines
vim /etc/yum.repos.d/CentOS-Vault.repo
[c5.11-base]
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
gpgcheck=1
name=CentOS-5.11 - Base
baseurl=http://vault.centos.org/5.11/os/$basearch/
exclude=ruby* libyaml* corosync* corosynclib* pacemaker*
enabled=1
[c5.11-updates]
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
gpgcheck=1
name=CentOS-5.11 - Updates
baseurl=http://vault.centos.org/5.11/updates/$basearch/
exclude=ruby* libyaml* corosync* corosynclib* pacemaker*
enabled=1
original link :- https://docs.onapp.com/misc/eol-centos-5-x