Designated Routers and Topology Support
DRs minimize topology traffic, but a DR works under the assumption that it is in contact with all devices. Multiaccess topologies, such as those found in NBMA and broadcast OSPF network types, rely on DRs and so are best applied to full-mesh topologies. If the topology is not a full mesh, then the DR should be manually selected, using priorities, to be a router with permanent virtual circuits (PVCs) connecting it to all other routers. For example, in a hub-and-spoke topology ..
EIGRP uses a sophisticated metric that considers bandwidth, load, reliability, and delay. That metric is Although this equation looks intimidating, a little work will help you understand the math and the impact the metric has on route selection. You first need to understand that EIGRP selects path based on the fastest path. To do that it uses K-values to balance bandwidth and delay. The K-values are constants that are used to adjust the relative contribution of t..
Packet-Switching Links: Frame Relay
Frame Relay was initially developed by the American National Standards Institute (ANSI) in 1984. Cisco Systems undertook major redevelopment of Frame Relay in 1990. StrataCom (now part of Cisco Systems), Northern Telecom, and Digital Equipment Corporation formed a consortium to focus on the development of Frame Relay technology. This consortium developed some additional features for the internetworking environment. Frame Relay is a packet-switching technology th..
Catalyst switches can support port-based authentication, a combination of AAA authentication and port security. This feature is based on the IEEE 802.1x standard. When it is enabled, a switch port will not pass any traffic until a user has authenticated with the switch. If the authentication is successful, the user can use the port normally. For port-based authentication, both the switch and the end user’s PC must support the 802.1x standard, using the Extensible Aut..
As we discuss in Appendix B, one of the most important things you can do to improve router performance, and consequently network performance, is to ensure that you are using the best packet switching algorithm. All Cisco routers support Fast Switching, and it is enabled by default. However, some types of configurations require that it be disabled. The following example shows how to turn Fast Switching back on if it has been disabled: Router#configure terminal Enter configura..
