Even with the most stable of software, it is sometimes necessary to upgrade to provide for new features or to fix a minor bug. In your network, this type of upgrade should be simple and should not impact your high availability, but it seems that in most networks, software upgrades are a Sisyphean task that diverts the attention of one or more network engineers from normal operations to the task of developing upgrade implementation and testing plans. When upgrading the operating system of your networking equipment, it is necessary to do the following:
Determine which set of networking features is required in the deployed device, such as IPv6, Multiprotocol Label Switching (MPLS), or certain routing protocols.
Determine which version of networking software is required to provide the fixes and features necessary. Versioning information can include:
Major release number
Minor release number
Maintenance release number
Software train, including general deployment, early deployment, special release, or deferred release (none of which apply to JUNOS releases)
Determine whether the hardware onto which the software is to be loaded has the proper amount of memory and processing power, and the correct firmware and hardware versions.
Determine whether the software release supports all the hardware versions in the device onto which the software is to be loaded, and whether it is interoperable with the devices ...