What provisions should be in place for network failure with minimal disruption to LabTutor?

The ideal solution is to have a plan in place with your IT department to quickly get the network active again in the event of failure. Provided power is still available to the lab, reliable ethernet should be achievable, thus allowing LabTutor Server to operate. Provisions should involve having spare components to replace those that are likely to fail - for example, switches, network cards and patch cables. Users could also have redundancy in place for essential services like LabTutor Server, DNS Servers and DHCP servers so that another server can take their place temporarily should they fail.
If the link between the lab and the server is most likely to fail, then providing a server physically located within the lab might be the only option to have good reliability.  

This information is valid for LabTutor v4.0 and later.