CLI Reference Guide-R07

Glossary
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TACACS+ Terminal Access Controller Access Control System Plus. TACACS+ is a logon authentication
protocol that uses software running on a central server to control access to TACACS-
compliant devices on the network.
TCP/IP Transmission Control Protocol/Internet Protocol. Protocol suite that includes TCP as the
primary transport protocol, and IP as the network layer protocol.
Telnet Defines a remote communication facility for interfacing to a terminal device over TCP/IP.
TFTP Trivial File Transfer Protocol. A TCP/IP protocol commonly used for software downloads.
UDP User Datagram Protocol. UDP provides a datagram mode for packet-switched
communications. It uses IP as the underlying transport mechanism to provide access to IP-
like services. UDP packets are delivered just like IP packets – connection-less datagrams that
may be discarded before reaching their targets. UDP is useful when TCP would be too
complex, too slow, or just unnecessary.
UTC Universal Time Coordinate. UTC is a time scale that couples Greenwich Mean Time (based
solely on the Earth’s rotation rate) with highly accurate atomic time. The UTC does not have
daylight saving time.
VLAN Virtual LAN. A Virtual LAN is a collection of network nodes that share the same collision
domain regardless of their physical location or connection point in the network. A VLAN
serves as a logical workgroup with no physical barriers, and allows users to share
information and resources as though located on the same LAN.
VRRP Virtual Router Redundancy Protocol uses a virtual IP address to support a primary router
and multiple backup routers. The backups can be configured to take over the workload if
the master fails or to load share the traffic. The primary goal of VRRP is to allow a host device
which has been configured with a fixed gateway to maintain network connectivity in case
the primary gateway goes down.
XModem A protocol used to transfer files between devices. Data is grouped in 128-byte blocks and
error-corrected.