CCNA Cisco Certified Network Associate Study Guide - FTP Server

706 Glossary
span A full-duplex digital transmission line connecting two facilities.
SPAN Switched Port Analyzer: A feature of the Catalyst 5000 switch,
offering freedom to manipulate within a switched Ethernet environment by
extending the monitoring ability of the existing network analyzers into the
environment. At one switched segment, the SPAN mirrors traffic onto a predetermined
SPAN port, while a network analyzer connected to the SPAN
port is able to monitor traffic from any other Catalyst switched port.
spanning explorer packet Sometimes called limited-route or single-route
explorer packet, it pursues a statically configured spanning tree when
searching for paths in a source-route bridging network. See also: all-routes
explorer packet, explorer packet, and local explorer packet.
spanning tree A subset of a network topology, within which no loops
exist. When bridges are interconnected into a loop, the bridge, or switch,
cannot identify a frame that has been forwarded previously, so there is no
mechanism for removing a frame as it passes the interface numerous times.
Without a method of removing these frames, the bridges continuously forward
them—consuming bandwidth and adding overhead to the network.
Spanning trees prune the network to provide only one path for any packet.
See also: Spanning-Tree Protocol and spanning tree algorithm.
spanning-tree algorithm (STA) An algorithm that creates a spanning
tree using the Spanning-Tree Protocol (STP). See also: spanning-tree and
Spanning-Tree Protocol.
Spanning-Tree Protocol (STP) The bridge protocol (IEEE 802.1d)
that enables a learning bridge to dynamically avoid loops in the network
topology by creating a spanning tree using the spanning-tree algorithm.
Spanning-tree frames called bridge protocol data units (BPDUs) are sent and
received by all switches in the network at regular intervals. The switches participating
in the spanning tree don’t forward the frames; instead, they’re processed
to determine the spanning-tree topology itself. Cisco Catalyst series
switches use STP 802.1d to perform this function. See also: BPDU, learning
bridge, MAC address, spanning tree, and spanning-tree algorithm.
SPF Shortest Path First algorithm: A routing algorithm used to decide on
the shortest-path spanning tree. Sometimes called Dijkstra’s algorithm and
frequently used in link-state routing algorithms. See also: link-state routing
algorithm.