CCENT/CCNA Icnd2 Chapt. 8

Link-state protocols collect information about the internetwork in the form of LSAs, which sit in memory in the link-state database. The router then runs the SPF algorithm to calculate that router’s best metric route to reach each subnet.

Distance vector protocols rely on periodic full routing updates from their neighbors to confirm that the neighbor is still working.

Route poisoning means advertising the failed route with an “infinite” metric, as opposed to simply ceasing to advertise the route. Poison reverse is route poisoning by advertising a route that previously was not advertised because of split horizon.

Split horizon causes a router to not advertise routes out an interface if the route would cause packets to be sent out that same interface.

OSPF (Open Shortest Path First) and Integrated IS-IS (Intermediate System to Intermediate System) are the routing protocols that are considered to use link-state logic. Link-state routing protocols build a complete topology map of the network by exchanging information about the state of their links with neighboring routers. This information is then used to calculate the shortest path to a destination. RIP-1, RIP-2, and EIGRP are distance-vector routing protocols, which do not use link-state logic.

Link-state protocols reflood each LSA on a periodic but longer timer. With RIP, the update timer is 30 seconds, and with OSPF, the timer is 30 minutes.

RIP-1 and RIP-2 are considered to use distance vector logic. Distance vector routing protocols determine the best path to a destination by considering the distance or metric to that destination. RIP-1 and RIP-2 use the hop count as the metric to determine the best path. They exchange routing information with neighboring routers and update their routing tables accordingly. EIGRP, OSPF, and Integrated IS-IS, on the other hand, use link-state logic where routers exchange information about the state of their links to determine the best path.

RIP-2, EIGRP, OSPF, and Integrated IS-IS support VLSM. VLSM (Variable Length Subnet Mask) allows for the creation of subnets with different subnet mask lengths within a network. RIP-1 does not support VLSM as it only uses classful routing, which means all subnets within a network must have the same subnet mask. However, RIP-2, EIGRP, OSPF, and Integrated IS-IS are classless routing protocols that can accommodate VLSM by allowing for the use of different subnet mask lengths for different subnets within a network.

EIGRP and OSPF are the routing protocols that use a metric that is, by default, at least partially affected by link bandwidth. EIGRP uses the bandwidth, delay, reliability, load, and MTU to calculate its metric, with bandwidth being one of the factors. OSPF uses the cost metric, which is inversely proportional to the bandwidth of the link. Both protocols take into consideration the link bandwidth in their metric calculations, making them suitable for determining the best path for routing traffic.

The router should not immediately send a full update. Instead, distance vector protocols immediately send a partial routing update, listing just the poisoned route.