GestióIP is an automated, Web based IPv4/IPv6 address management (IPAM) software. It features powerful network discovery functions and offers search and filter functions for both networks and host, permitting Internet Search Engine equivalent expressions. This lets you find the information that administrators frequently need easily and quickly. GestióIP also incorporates an automated VLAN management system.
netcat with its simple and yet incredibly powerful command line constructs has helped me innumerable times to validate TCP and UDP end to end connectivity
The Dude network monitor is a new application by MikroTik which can dramatically improve the way you manage your network environment. It will automatically scan all devices within specified subnets, draw and layout a map of your networks, monitor services of your devices and alert you in case some service has problems.