FastEther Channel (FEC) is a Cisco method that bundles 100 Mbps FAST ETHERNET ports into a logical link. Because any redundant paths between two switches mean some ports will be in a blocking state and bandwidth will be reduced, Cisco developed FEC to maximize bandwidth use. Figure 2-4 displays a switched network with two 100-Mbps connections between them. Because of STP, the link will be in a blocking state after the election of a root bridge, Switch A, in this case. Switc..
Like an OSPF designated router (DR), an IS-IS DIS exists to simulate a point-to-point topology across a multipoint environment. Because of this, a DIS is sometimes called a pseudonode. Despite their similarities, the IS-IS DIS is subtly different from OSPF. The DIS exists separately at Level 1 and Level 2, and there is not a backup DIS. An OSPF DR is elected for life; IS-IS allows preemption if another router comes on line with a higher priority. Fewer adjacencies are..
IGMPv1 Solicited Host Membership Report
Figure 19-9 shows operation of the IGMPv1 Solicited Host Membership Report process and the Report Suppression mechanism. Figure 19-9 picks up the example from Figure 19-8, in which router R1 had sent an IGMPv1 Query. Figure 19-9 IGMPV1 Solicited Host Membership Report and Report Suppression Processes If many hosts have launched multicast applications and if all of them respond to the Host Membership Query with the Host Membership Report, too many redundant reports wou..
QoS Requirements of the Control Plane
Unless the network is up, QoS is irrelevant. Therefore, it is critical to provision QoS for control-plane traffic, which includes IP routing traffic and network management. IP Routing When addressing the QoS needs of IP routing traffic, the following guidelines are recommended: • IP routing traffic should be marked to DSCP CS6; this is default behavior on Cisco IOS platforms. • Interior gateway protocols usually adequately are protec..
A campus network’s core layer provides connectivity of all distribution-layer devices. The core, sometimes referred to as the backbone, must be capable of switching traffic as efficiently as possible. Core devices, sometimes called campus backbone switches, should have the following attributes: ■ Very high throughput at Layer 3 ■ No costly or unnecessary packet manipulations (access lists, packet filtering) ■ Redundancy and resilience for high availability ■ Advanc..
