1.
Which of the following routing protocols are considered to use distance vector logic?
Correct Answer(s)
A. RIP-1
B. RIP-2
Explanation
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.
2.
Which of the following routing protocols are considered to use link-state logic?
Correct Answer(s)
D. OSPF
E. Integrated IS-IS
Explanation
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.
3.
Which of the following routing protocols use a metric that is, by default, at least partially affected by link bandwidth?
Correct Answer(s)
C. EIGRP
D. OSPF
Explanation
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.
4.
Which of the following interior routing protocols support VLSM?
Correct Answer(s)
B. RIP-2
C. EIGRP
D. OSPF
E. Integrated IS-IS
Explanation
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.
5.
Which of the following situations would cause a router using RIP-2 to remove all the routes learned from a particular neighboring router?
Correct Answer
B. No longer receiving updates from that neighbor
Explanation
Distance vector protocols rely on periodic full routing updates from their neighbors to confirm that the neighbor is still working.
6.
Which of the following distance vector features prevents routing loops by causing the routing protocol to advertise only a subset of known routes, as opposed to the full routing table, under normal stable conditions?
Correct Answer
D. Split horizon
Explanation
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.
7.
Which of the following distance vector features prevents routing loops by advertising an infinite metric route when a route fails?
Correct Answer
D. Route poisoning
Explanation
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.
8.
A router that is using a distance vector protocol just received a routing update that lists a route as having an infinite metric. The previous routing update from that neighbor listed a valid metric. Which of the following is not a normal reaction to this scenario?
Correct Answer
D. Send a full update listing a poison route for the failed route
Explanation
The router should not immediately send a full update. Instead, distance vector protocols immediately send a partial routing update, listing just the poisoned route.
9.
An internetwork is using a link-state routing protocol. The routers have flooded all LSAs, and the network is stable. Which of the following describes what the routers will do to reflood the LSAs?
Correct Answer
B. Each router refloods each LSA using a periodic timer that is much longer than distance vector update timers
Explanation
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.
10.
Which of the following is true about how a router using a link-state routing protocol chooses the best route to reach a subnet?
Correct Answer
B. The router calculates the best route by running the SPF algorithm against the information in the link-state database.
Explanation
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.