Identifying Neighbors and Defining Peer Groups
BGP does not promiscuously attach to other routers—neighbors must be predefined. The neighbor command is used to identify each neighbor and its AS. If the neighbor AS is the same as this router's AS then this is an iBGP connection. If the AS is different, this is an external neighbor. After the neighbor is defined, further neighbor commands are used to describe the policy used to filter routes to the neighbor. Router(config-router)#neighbor ip-address remote-as auto..
As OSPF link-state information is shared between areas, an intricate set of mechanisms is followed, relying on a number of different OSPF packet types. All OSPF traffic is transmitted inside IP packets. Receivers recognize OSPF traffic because it is marked as IP protocol 89. OSPF includes five packet types: • Hello packets— Establish communication with directly attached neighbors. • Database Descriptor (DBD)— Sends a list of router IDs from..
Maintaining the Topology Table
The topology table may be recalculated because a new network is added to the network, successors change, or because a network is lost. Figure 3-4 illustrates the traffic flow seen when a router loses a connection. Figure 3-4. Traffic Flow Used to Maintain the Topology Table Just as the neighbor table tracks the receipt of the EIGRP packets, the topology table records the packets that have been sent by the router to the neighbors. It also identifies the status of the ..
IP prefixes from each routing process are inserted in the central forwarding information base (FIB). This is the routing table used for actual packet forwarding. When there are two equal-length prefixes from the different RIBs or different routing processes or protocols, an administrative distance is applied to break the tie. This distance typically is applied to the whole routing process—with the notable exception being BGP, which has different administrative distances for..
FCAPS (fault, configuration, accounting, performance and security), the ISO model for network management, is a functional approach that segments management areas into discrete categories, which allows the network manager or management framework to address each in turn and ensure that no area is overlooked. FCAPS is a model, not a product. Many network management applications and designs adopt FCAPS, and internally developed procedures and tools can also be architected along t..
