managers who wish to view baseline performance statistics without diverting existing tools. Alternatively, SNMP alarms generated by managed taps can alert network managers to link conditions that merit examination by analyzers to intrusion detection systems. Some taps get some of their power (i.e., for the pass-through) or all of their power (i.e., for both pass-through and monitor) from the network itself. These can be referred to as having inline power. Some taps can also reproduce low-level network errors, such as short frames, bad CRC or corrupted data. Advantages of a network tap Here are some advantages of a network tap over port mirroring or SPAN: Passive; fail-safe Zero configuration Secure Exact duplicate of network traffic No added latency or altered timing Passes network errors in addition to good frames/packets Oversubscription not an issue Disadvantages and problems Because network taps require additional hardware, they are not as cheap as technologies that use capabilities that are built into the network. However, network taps are easier to manage and normally provide more data than some network devices. Network taps can require channel bonding on monitoring devices to get around the problem with full-duplex discussed above. Vendors usually refer to this as aggregation as well. Putting a network tap into place will disrupt the network being monitored for a short time. Even so, a short disruption is preferable to taking a network down multiple times to deploy a monitoring tool. Establishing good guidelines for the placement of network taps is recommended. Monitoring large networks using network taps can require a lot of monitoring devices. High-end networking devices often allow ports to be enabled as mirror ports, which is a software network tap. While any free port can be configured as a mirror port, software taps require configuration and place load on the network devices. Even fully passive network taps introduce new points of failure into the network. There are several ways that taps can cause problems, and this should be considered when creating a tap architecture. Consider non-powered taps for optical-only environments or throwing star network tap for copper 100BASE-TX. This allows you to modify the intelligent aggregation taps that may be in use and avoids any complications when upgrading from 100 megabit to gigabit to 10 gigabit. Redundant power supplies are highly recommended. Fully passive is only possible on optical connections of any bandwidth and on copper connections from type G703 (2Mbit) and