ccna 200 301 syllabus plural form of roof

ccna 200 301 syllabus plural form of roof.. Route poisoningRoute poisoning implies unreachability of a network by setting the number of hops on the failed network to the maximum number of hops plus one. Poisonreverse is another way to avoid routing loops. once a route has been learned from an interface. then that route is sent back as an unreachable route from the same interface. In Figure 5-5-1, after Network 1 on Router A is disconnected, route poisoning causes Router A to announce to Router B that the metric for Network 1 is the maximum number of hops plus 1,which, for the RIP protocol, is 16^o Router B receives a message from Router A and knows that Network 1 has 16 hops, implying that Network 1 is unreachable and needs to be removed from this path. Toxicity inversion causes Router B to send back a message that Network 1 is unreachable in the direction of the learned Network 1 route, i.e., Router A. Route poisoning or toxic inversion is used to overcome large network routing loops.If route poisoning is not used and a router with a topology change, such as Router A in Figure 5-5.1, detects the loss of directly connected route Network 1, Router A will not include Network 1 in its update packets to Router B. Occasionally an update packet does not include Network 1, Router B does not assume that Network 1 has failed, Router B assumes that Network 1 is still valid and continues to send it to Routers C and E. Router B considers Network 1 to be still valid and continues to send it to Router C and Router E. Router B considers Network 1 invalid when multiple update packets in a row contain no information about Network 1. In the RIP protocol, this value defaults to 180 seconds, which is six consecutive update packet times. Similarly, Router C and Router E take another roughly 180 seconds to realize that Network 1 is unreachable, so the route will take longer to converge. If route poisoning is used, Router A sends an update packet to Router B that contains Network 1 for 16 hops, implying that Network 1 is unreachable. The poisoning reversal is when Router B in turn tells Router A that Network 1 is unreachable. Reach. Of particular note here is that toxic inversion is unaffected by horizontal segmentation. For more information about RIP-related timers, see the next chapter in Section 6.3.. Triggered updates (TRIGGERED UPDATES)Distance vector routing protocols generally occur periodically for routing updates, for example, RIP is 30 seconds, and updates are not sent even if the route has changed before the update period. In contrast, link-state routing protocols are generally triggered updates, sending route updates as soon as there is a topology change. By using triggered updates in distance vector routing protocols, there is no need to wait for the update timer to expire before sending the update, so that the update is quickly transmitted across the network, reducing the possibility of routing loops.. Suppression timers (holddowntime) can be used to avoid the problem of counting to infinity. The use of the suppression timer is divided into the following four cases:If a router receives an update from a neighbor indicating that a previously reachable network is now unreachable, this router marks the route as unreachable and also starts a suppression timer, such as RIP default of 180 seconds. If an update indicating that the network is reachable again is received from the same neighbor before the suppression timer expires, this router151/Chapter 5 Routing Protocols*** I05marks this network as reachable and removes the suppression timer.