Modifique el archivo /etc/yum.repos.d/CentOS-Base.repo
Con la sig. config.
[base]
name=CentOS-$releasever - Base
#mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://vault.centos.org/5.11/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
exclude=redhat-logos php53*
#released updates
enabled=1
[updates]
name=CentOS-$releasever - Updates
#mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://vault.centos.org/5.11/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
exclude=redhat-logos php53*
#additional packages that may be useful
enabled=1
[extras]
name=CentOS-$releasever - Extras
#mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://vault.centos.org/5.11/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
exclude=redhat-logos php53*
#additional packages that extend functionality of existing packages
enabled=1
[centosplus]
name=CentOS-$releasever - Plus
#mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
baseurl=http://vault.centos.org/5.11/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
exclude=redhat-logos php53*
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
#mirrorlist=http://vault.centos.org/?release=$releasever&arch=$basearch&repo=contrib
baseurl=http://vault.centos.org/5.11/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5
exclude=redhat-logos php53*
Pero obtengo este error (No me permite instalar Addons desde la web de elastix)
Could not retrieve mirrorlist http://mirror.elastix.org/?release=2&arch=i386&repo=commercial_addons error was
[Errno 4] IOError: <urlopen error (113, 'No route to host')>
Error: Cannot find a valid baseurl for repo: commercial-addons