Check that a physical link is up with the proper speed
This check is great to detect when a network cable for whatever reason deteriorates and stops providing the desired up-link speed. It works perfectly for any system that has ethtool installed.
This particular check has helped me as a sysadmin to detect bad quality cables that, after being reused many times, end up deteriorating and do not let me get 1Gbps in RJ-45 CAT 5E cables. I have also been able to detect network card failures, and also malfunctioning switch ports.
Check that an FTP account is fully working
This script uses lftp, a sophisticated ftp/http client, to check not only that a give FTP account is accessible, but that it is also able to list files and directories, to get and put files and to delete files. This simple script is fast, easy to configure, flexible and can be extended easily.
Sometimes, things like SELinux, a failed network mount point or wrong permissions cause an FTP account to not work properly. With this check, you will be able to detect it immediately.