Ethernet bridging essentially involves combining an ethernet interface with one or more virtual TAP interfaces and bridging them together under the umbrella of a single bridge interface. Ethernet bridges represent the software analog to a physical ethernet switch. The ethernet bridge can be thought of as a kind of software switch which can be used to connect multiple ethernet interfaces (either physical or virtual) on a single machine while sharing a single IP subnet. By bridging a physical ethernet NIC with an OpenVPN-driven TAP interface at two separate locations, it is possible to logically merge both ethernet networks, as if they were a single ethernet subnet.
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
Computer monitoring systems are used to gather data for the purpose of real-time incident notification, performance analysis, and system health verification. Without such a tool, a system administrator would have to login to each machine to collect information on a regular basis. This kind of repetitive task can be automated using a system monitoring tool. System monitoring can also help identify problems before they escalate to emergency status. This type of software is not only useful for network administrators. Home users with a small network or even just a single computer will benefit from advanced notification provided by system monitoring tools. Knowing that free space on the hard disk is running out, or that a particular server/daemon has gone down can be extremely useful.
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.