In order for a router to route data, what must that router determine?A. the route age of the next-hop deviceB. the subnet mask of the source networkC. the cost metric of the path of the destinationD. the outbound interface of the best path to the destination
Ans: D

Explanation: In order to route the data to the correct destination the router must know the
outbound interface that provides the best destination.
The other alternatives do no apply.


# QUESTION 2
Which of the following statements is true regarding the routing tables on a Cisco router?A. Entries are listed in the order of the route cost metric.B. Only the active link is shown for load-balanced routers.C. Privileged EXEC mode is required to view the routing table.D. The clear ip route * command refreshes the entire routing table.
Ans: C

Explanation: The show ip route command is used to display IP routing table entries. It can only
be run in privileged (enable) mode.
Incorrect Anss
A: Entries are not listed in route cost order.
B: The other links in the load balanced bundle are also shown.
D: The clear ip route command is used the clear delete IP routing table entries. In particular the
clear ip route * (or clear ip route all) command delete IP routing table entries. This is not a
refresh. Static routes will not be recreated.


# QUESTION 3
Which of the following phrases is the correct term for what happens to a network when a
topology change causes all the routers to synchronize their routing tables?A. floodingB. broadcastingC. convergenceD. summarization
Ans: C

Explanation: A topology change forces a convergence of the routers to a new routing state.
Convergence is the time that it takes for all routers to agree on the network topology after a
change.


Section 2: Describe classful and classless routing protocols (3 Questions)


Q
You are a guest lecturer at the CertKing academy when one of your students asks you to
define classless routing protocols in one sentence. How would you respond?A. A default gateway is required.B. Variable-length subnet masks are not supported.C. Routers are automatically summarized to class boundaries.D. Networks with different subnet masks can exist in the same address class.
Ans: D

Explanation: Classless routing protocols understand that different routes within a major network can
have different masks.
Incorrect Anss
A: There is no requirement for a default gateway.
B: Classless routing protocols advertise the routing mask for each route. This enables VLSM (variable
length subnet masks).
C: With class routing the summarization process is manually controlled and can be invoked at
any point within the network. It is not limited to class boundaries.


# QUESTION 2
What are two advantage of implementing a classless routing protocol? (Select two)A. Support for VLSM.B. Support for FLSM.C. Summarization of discontinuous subnets.D. Auto-summarization across network boundaries.E. The ip classless command improves convergence.
Ans: A, C

Explanation:A. Classless routing protocols support VLSM, and that, in turn, leads to more efficient
allocation of subnet masks to meet different host requirements on different subnetworks,
resulting in better utilization of host addresses.C. Because subnets routes are propagated throughout the routing domain, summarization is
often required to keep the routing tables at a manageable size.
Reference: Building Scalable Cisco Networks (Ciscopress) page 19 + 20


# QUESTION 3
Which three of the following routing protocols are classless routing protocols? (Select
three)A. IS-ISB. IGRPC. RIPv1D. OSPFE. EIGRP
Ans:A. D, E

Explanation: IS-IS, Open Shortest Path First (OSPF) and Enhanced IGRP are all classless
routing protocols.
Note: RIPv2 and BGP are also classless routing protocols.
Incorrect Anss
B, C: IGRP and RIPv1 are not classless.


Section 3: Describe link-state router protocol operation (3 question)


Q
You are a senior network administrator hard at work when one of your junior
administrators storms into your office asking you if you can describe to her what a link
state routing protocol is. How would you Ans her?A. Link-state protocols do not support summarization.B. Static routes must be used to accommodate link redundancy.C. All routers in the area know when another router joins the area.D. Link-state protocols utilize spanning tree to propagate routing changes.
Ans: C

Explanation: All routers within an area will have the same view of the area - they will all have
the same topology table. All of them will know when another router joins the area.
Incorrect Anss
A: Link State protocols support route summarization.
B: Link redundancy does not require use of static routes.
D: The spanning tree is not to propagate routing changes. Instead it used to find the shortest path
to the destinations.


# QUESTION 2
Which of the following statements best describes link-state protocols?A. Link state protocols periodically multicast the Link State Advertisements at 90 second
intervals.B. Link state routing protocols use Hello packets to build the link state database.C. Link state routing protocols use poison reverse and holddown timer to prevent routing
loops.D. Link state routing protocols use Link State Advertisements to announce route changes.
Ans: B

Explanation:
The Hello Protocol
The Hello Protocol is responsible for establishing and maintaining neighbor relationships. It also
ensures that communication between neighbors is bidirectional. Hello packets are sent
periodically out all router interfaces.
The router sends hello packets to its neighbors and receives their hello packets. In addition to
helping acquire neighbors, hello packets also act as keepalives to let routers know that other
routers are still functional. Topological databases are synchronized between pairs of adjacent
routers.


# QUESTION 3
In a link-state environment, what does the router do when a route flaps?A. It enters the exstart state with its neighbors.B. It floods the area with new routing information.C. It generates a routing exchange using the hello protocol.D. It waits for the holdown timers to expire and then sends an update.
Ans: B


Section 4: Compare classful and classless routing protocols (1 questions)


Q
Which one of the statements below regarding classful and classless routing protocols is
correct?A. In a classful system, a router uses a bit mask to determine the network and host portions
of an address and there is no class restriction.B. In a classless system, a router determines the class of an address and then identifies the
network and host octets based on that class.C. In a classful system, subnet mask information is maintained and passed along with each
routing update.D. In a classless system, when a routing update is received about a different major network
as configured on the receiving interface, the default subnet mask is applied.E. In a classful system, when a routing update is received about the same major network as
configured on the receiving interface, the router applies the subnet mask configured on
the receiving interface.
Ans: A

Explanation:
Classless routing protocols understand that different routes within a major network can have different
masks.B. Classless routing protocols support VLSM, and that, in turn, leads to more efficient
allocation of subnet masks to meet different host requirements on different subnetworks,
resulting in better utilization of host addresses.D. Because subnets routes are propagated throughout the routing domain, summarization is
often required to keep the routing tables at a manageable size.


Section 5: Compare distance vector and link state routing protocols (8 Questions)

Q
You're a systems administrator who's just chosen OSPF over RIP. Your junior
administrator Britney is confused and asks you why you didn't choose RIP. What would
you tell her?A. OSPF maintains smaller routing tables.B. OSPF cost metric is based on number of hops.C. OSPF only sends routing updates when necessary.D. OSPF VLSM allows more efficient use of IP addresses.
Ans: C, D

Explanation:
C: RIP use periodic broadcast of the entire routing table, while OSPF use event-triggered
announcements.
D: RIP Version 1 does not support VLSM.
Incorrect Anss
A: The size of the routing table is of the same magnitude.
B: RIP uses hop as cost metric.


# QUESTION 2
OSPF is the popular choice as the standard open routing protocol. Why is it more popular
then RIPv1 & RIPv2?A. Greater CUP overhead.B. Greater router memory requirements.C. Greater scalability.D. Simpler distance vector algorithm.E. Simpler configurationF. Simpler route selection.
Ans: C F

Explanation:
o Support for variable length subnet masks (VLSMs)
o Method for path selection
Reference: Building Scalable Cisco Networks (Ciscopress) page 99 + 100