Introduction to networking Dynamic routes

Objectives  Define dynamic routing and its properties  Describe the classes of routing protocols  Describe the basic router configuration commands for protocols

Dynamic routing overview  Dynamic routing allow routers to learn about remote networks fro mother routers and update their own routing tables with new information  Dynamic routing is necessary to allow networks to update and adapt quickly to changes  The success depends on the maintenance of a routing table and timely distribution of knowledge  Dynamic routing depends on routing protocols which describe:  How to send updates  What knowledge is contained in these updates  When to send this knowledge  How to locate recipients of the updates  Administrative distance is used to determine the preferred source of routing updates

Routing protocols

Identifying the classes of interior gateway routing protocols Determines direction, or vector (exit interface), and Distance (metric) to any link in the internetwork Recreates the exact topology of the entire internetnetwork

Distance vector Each router receives a routing table from its directly connected neighbour routers. The distance vector algorithm (Bellman-Ford) does not allow a router to know the exact topology of an internetwork since each router only sees its neighbor routers.

Distance vector network discovery The interface that leads to each directly connected network has a distance of 0

Distance vector network discovery An analogy of distance vector could be the signs found at a highway intersection. A sign points toward a destination and indicates the distance to the destination. Further down the highway, another sign points toward the destination, but now the distance is shorter. As long as the distance is shorter, the traffic is on the best path.

Link state routing protocol features Link-state advertisement (LSA) - a small packet of routing information that is sent between routers Topological database - a collection of information gathered from LSAs SPF algorithm - a calculation performed on the database that results in the SPF tree Routing table - a list of the known paths and interfaces Consists of all LSA’s

Shortest path calculations

Link state topology changes

Link state concerns

Routing configuration GAD(config)#router rip GAD(config-router) #network IP network number of directly connected network

Configure EIGRP  To configure EIGRP on a router  router(config)#router eigrp autonomous-system  router(config)#router eigrp 1  An autonomous system is a collection of networks under a common administrative control  EIGRP uses a autonomous system number, but calls this a process ID  The process ID essentially refers to an instance of the protocol running on a router  All the routers running in the same routing domain that are using EIGRP must have the same process ID in order to communicate

Configure EIGRP with a network address  router(config)#router eigrp 1  router(config)#network

EIGRP wildcard masks  The command:  router(config)#eigrp 1  Router(config)#network will activate EIGRP on all interfaces in the network  There may be a reason not to have EIGRP activated on all interfaces, or basically to disable EIGRP on some interfaces  router(config)#network network-address [wildcard mask]

EIGRP wildcard masks  Think of a wildcard mask is the inverse of a subnet mask  E.g. The inverse of is  To work out the inverse, subtract the subnet mask from  E.g =  router(config)#network

Summary  Dynamic routing scales better to larger, more complex networks  They involve more complex protocols that demand a greater knowledge of networking

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