Netgear XCM8806 Chassis User Manual - Page 942

NETGEAR 8800 User Manual S (Continued) STP STPD STPD mode stub areas system health check T TACACS+ tagged VLAN TCN Spanning Tree Protocol. STP is a protocol, defined in IEEE 802.1d, used to eliminate redundant data paths and to increase network efficiency. STP allows a network to have a topology that contains physical loops; it operates in bridges and switches. STP opens certain paths to create a tree topology, thereby preventing packets from looping endlessly on the network. To establish path redundancy, STP creates a tree that spans all of the switches in an extended network, forcing redundant paths into a standby, or blocked, state. STP allows only one active path at a time between any two network devices (this prevents the loops) but establishes the redundant links as a backup if the initial link should fail. If STP costs change, or if one network segment in the STP becomes unreachable, the spanning tree algorithm reconfigures the STP topology and re-establishes the link by activating the standby path. Spanning Tree Domain. An STPD is an STP instance that contains one or more VLANs. The switch can run multiple STPDs, and each STPD has its own root bridge and active path. In the NETGEAR implementation of STPD, each domain has a carrier VLAN (for carrying STP information) and one or more protected VLANs (for carrying the data). The mode of operation for the STPD. The two modes of operation are: • 802.1d-Compatible with legacy STP and other devices using the IEEE 802.1d standard. • 802.1w-Compatible with Rapid Spanning Tree (RSTP). In OSPF, a stub area is connected to only one other area (which can be the backbone area). External route information is not distributed to stub areas. The primary responsibility of the system health checker is to monitor and poll error registers. In addition, the system health checker can be enabled to periodically send diagnostic packets. System health check errors are reported to the syslog. Terminal Access Controller Access Control System. Often run on UNIX systems, the TACAS+ protocol provides access control for routers, network access servers, and other networked computing devices via one or more centralized servers. TACACS+ provides separate authentication, authorization, and accounting services. User passwords are administered in a central database rather than in individual routers, providing easily scalable network security solutions. You identify packets as belonging to the same tagged VLAN by putting a value into the 12-bit (4 octet) VLAN ID field that is part of the IEEE 802.1Q field of the header. Using this 12-bit field, you can configure up to 4096 individual VLAN addresses (usually some are reserved for system VLANs such as management and default VLANs); these tagged VLANs can exist across multiple devices. The tagged VLAN can be associated with both tagged and untagged ports. Topology change notification. The TCN is a timer used in RSTP that signals a change in the topology of the network. 942 | Appendix E. Glossary