Many organisations use a three tier support staff solution, with tier one (help desk) personnel handling the initial calls, tier 2 (technicians and PC support analysts) and tier three (network administrators). Most of those organisations follow a fixed staffing ratio, and being a network administrator is either the top job, or next to top job, within the technical support department.
Network administrators are responsible for making sure computer hardware and the network infrastructure itself is maintained properly for an IT organisation. They are deeply involved in the procurement of new hardware (does it meet existing standardisation requirements? Does it do the job required?) rolling out new software installs, maintaining the disk images for new computer installs (usually by having a standardised OS and application install), making sure that licenses are paid for and up to date for software that need it, maintaining the standards for server installations and applications, and monitoring the performance of the network, checking for security breaches, poor data management practices and more.
Network Mapping Software
Most network administrator positions require a breadth of technical knowledge and the ability to learn the ins and outs of new networking and server software packages quickly. While designing and architecting a network is usually the job of a network engineer, many organisations roll that function into a network administrator position as well; day to day and month to month "Is it up?" jobs fall on the shoulders of the network administrators.
One of the chief jobs of a network administrator is connectivity; the cry "The networks down" usually means the network admin has to be hip deep in something fixing it and post haste. They are in charge of making sure connectivity works for all users in their organisation, and making sure data security is handled properly for connections to the outside internet. (For network administrators doing security aspects, this can be a full time job in and of itself.)
Trouble tickets work their way through the help desk, then through analyst level support, before hitting the network administrator level; as a result, in their day-to-day operations, they should not be dealing directly with end users as a routine function. Most of their jobs should be on scheduling and implementing routine maintenance tasks, updating disaster prevention programs, making sure that network backups are run and doing test restores to make sure that those restores are sound.
Other jobs that fall on the network administrator's tasks include fighting for the IT budget and setting standardised installs packages up so that all end user desktops are identical. While the network administrator probably isn't doing the installs on new computers, he is likely to be the one in charge of setting up what gets installed, and setting user access policies, as well as evaluating the purchase of new equipment to replace older gear that has been deployed. Similar decisions are made regarding software packages (both for end user support and server levels) and networking hardware.
Network administrators are jokingly referred to as the highest level of techie you get before you get turned into a pointy haired boss and made into management.
Network Administrator - Duties and Functions Network Mapping Software