24 What Is Routing? To route, a router needs to do the following: Know the destination addressIdentify the sources it can learn fromDiscover possible routesSelect the best routeMaintain and verify routing informationSlide 1 of 2Purpose: This figure introduces students to routing. The router must accomplish the items listed in the figure for routing to occur.Emphasize: Path determination occurs at Layer 3, the network layer. The path determination function enables a router to evaluate the available paths to a destination and to establish the best path.Routing services use network topology information when evaluating network paths. This information can be configured by the network administrator (static routes) or collected through dynamic processes (routing protocols) running in the network.Transition: How do you represent the path to the packet’s destination?
25 What Is Routing? (Cont.)Slide 2 of 2Purpose: This figure explains that routers must learn about paths that are not directly connected.Emphasize: The router already knows about directly connected networks. It must learn about those networks that are not connected. This chapter describes how routers learn about those paths.Routers must learn destinations that are not directly connected.
26 What Is a Routing Protocol? Routing protocols are used between routers to determine paths and maintain routing tables.Once the path is determined, a router can route a routed protocol.Purpose: This figure introduces students to routing protocols and compares routing protocols to routed protocols.Emphasize: If network wants to know about network , it must learn it from its S0 (or possibly S1) interface.Note: The two routing protocols that will be taught in this course are RIP and IGRP. They are both distance vector routing protocols.
29 Static RoutesPurpose: This figure describes how a static route operates.Emphasize: For intercommunication, static routes must be configured in both directions. Static routes are often used to route traffic to a stub network or other network where only a single route to that network exists.Configure unidirectional static routes to and from a stub network to allow communications to occur.
30 Static Route ExamplePurpose: This figure gives an example of a static route configuration.This is a unidirectional route. You must have a route configured in the opposite direction.
32 Default RoutesPurpose: This figure gives an example of a default route configuration.Emphasize: With an address and subnet mask of in the ip route statement, packets for any network not listed in the routing table will be sent to the next hop,This route allows the stub network to reach all known networks beyond router A.
76 Network layer devices combine multiple broadcast domains. Purpose: This figure shows a router on a stick being used to interconnect VLANs.Emphasize: The VLANs are on different networks. Without a network layer device they could not communicate.Review the protocols operating at each of the OSI layers.Network layer devices combine multiple broadcast domains.
77 Inter-VLAN Routing: Multiple Router Interfaces Multiple links between switch and router required to pass traffic between VLANs.
78 Dividing a Physical Interface into Subinterfaces Physical interfaces can be divided into multiple subinterfaces.Purpose: This figure shows a subinterface example. Subinterfaces will be covered later in this course.Emphasize: At this point, it is important for students to understand that if they want to connect multiple VLANs, they need a separate connection for each VLAN. This can be accomplished by establishing a physical connection for each VLAN that will interconnect with other VLANs, or by splitting a trunk into multiple, logical subinterfaces.
79 Routing Between VLANs with ISL Trunks Purpose: This figure shows the configuration of the router on a stick.Emphasize: Highlight the two different interconnecting networks, and
80 Routing Between VLANs with 802.1Q Trunks Purpose: This figure shows the configuration of the router on a stick.Emphasize: Highlight the two different interconnecting networks, and