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..
Understanding Level 1 and Level 2 Routing
In level 1, IS nodes are based on the ID portion of the address. All level 1 routers route within their own area. They recognize the destination within their area by reading the destination address. If the destination is within the same area, the packet is routed to the destination. If the destination is not within the same area, it is sent to the closest level 2 router. In IS-IS, all level 1 areas are stub areas, so no information is sent to level 1 routers tha..
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..
Settings That Must Match for OSPF Neighborship
After an OSPF router has discovered a potential neighbor by receiving a Hello from the other router, the local router considers the router that sent the Hello as a potential neighbor. The local router must examine the contents of the received Hello, plus a few other factors, compare those settings to its own, check for agreement, and only then may that other router be considered an OSPF neighbor. For reference, the following list details the items seen in OSPF He..
