If you are using a local repository for your CSN, and you need to upgrade to CentOS/ RHEL 6.8 for CSN 8.2, you may notice that some avahi packages are not available on disk 1 of the repo. They are only available on disk 2. We bundle the required avahi packages in the CSN 8.2 zip file, so if you would prefer to just install them locally instead of adding all of disk 2 (or adding the avahi packages to your local repo) you can do so easily.
Simply download the 8.2 CSN bundle to your CSN. Unzip the bundle. Install the three packages like this:
rpm -Uvh avahi-0.6.25-15.el6.x86_64.rpm --nodeps
rpm -Uvh avahi-tools-0.6.25-15.el6.x86_64.rpm --nodeps
rpm -Uvh avahi-libs-0.6.25-15.el6.x86_64.rpm --nodeps
After that, you will be able to run: yum update successfully to CentOS 6.8.
NOTE: Do not use yum update, as it will make you update past 6.8. See IMPORTANT: Prevent CSN from upgrading past CentOS 6.8.