about ccna routing and switching

about ccna routing and switching.For example, auto-cost reference-bandwidth 10000 adjusts the link to a speed of 10 Gbit/s. Tip: Cisco recommends that the same OSPF reference bandwidth should be set on all OSPF routers in an enterprise network.For ease of learning, the following list summarizes the rules for how a router sets its OSPF interface overhead.184 Chapter 8 Implementing IPv4 OSPFWords (1) Use the iP ospfcostx interface subcommand to explicitly set the overhead to a value between 1 and 65 535. including 1 and 65 535.I.b edit (2) Use the bandwidth speed command to modify the interface bandwidth. the speed is a number in kilobits per second (kbit/s).(3) Use the router OSPF subcommand auto-costreference-bandwidth ref-bw to modify the reference bandwidth,in megabits per second (Mbit/s).OSPF Load BalancingWhen a router uses SPF for several routes to calculate the metric of each route to a subnet, one of the routes may have the lowest metric, so OSPF puts that route into the routing table. However, if multiple routes to the same subnet have the same metric value, the router can put multiple equivalent routes into the routing table (four different routes by default) based on the setting of the maximum-paths number router subcommand. For example, if there are six possible paths between certain parts of the network in an interconnected network, and the engineer wants all routes to be used, the router configuration could be to use the maximum-paths 6 subcommand on the routerospfT side.A more challenging concept involves how the router uses these routes. A router performs load balancing of packets on a single packet basis. For example, if a router has three equivalent OSPF routes in its routing table that reach the same subnet, the router can send a packet in the first route, the next packet in the second route, the next packet in the third route, and then the fourth packet starts over from the first route. Alternatively, load balancing can be performed on a per-destination IP address basis.8.3 Exam Preparation