CCNP 642-901 BSCI - Building Scalable Cisco Internetworks Version 01.17.08 Part-2

CCNP 642-901 BSCI - Building Scalable Cisco Internetworks Version 01.17.08 Part-1
QUESTION 11:
A link failure in the Certkiller network has caused the EIGRP routers to update
their routing tables. What action does an EIGRP router take when it cannot find a
feasible successor for a network?
A. It examines the topology table for a next best path.
B. It transitions from passive to active state for that network and queries its neighbors.
C. It examines the routing and neighbor tables for the next best path.
D. It transitions from active to passive state for that network and queries its

neighbors.
E. None of the above
Answer: B
Explanation:
* Successor - A successor is a route selected as the primary route to use to reach a
destination. Successors are the entries kept in the routing table. Multiple successors for a
destination can be retained in the routing table.
* Feasible successor - A feasible successor is a backup route. These routes are selected
at the same time the successors are identified, but are kept in the topology table. Multiple
feasible successors for a destination can be retained in the topology table

QUESTION 12:
EIGRP performs automatic summarization at network boundaries. What
administrative distance is given to EIGRP summary routes?
A. 1
B. 90
C. 95
D. 0
E. 5
F. 170
G. 255
H. None of the above
Answer: E
Explanation:

EIGRP automatically summarizes routes at the classful boundary, the boundary where
the network address ends as defined by class-based addressing. In most cases, auto
summarization is a good thing, keeping the routing tables as compact as possible
In the presence of discontiguous subnetworks, automatic summarization must be disabled
for routing to work properly. To turn off auto-summarization, use the following
command:
Router(config-router)#no auto-summary
Default Administrative Distance

QUESTION 13:
You need to alter the metrics of certain EIGRP routes in the Certkiller network.
Which two parameters are used by default to compute the EIGRP metric? (Select
two)
A. MTU
B. bandwidth
C. delay
D. reliability
E. load
F. Interface up time
Answer: B, C
Explanation:

Metrics are the mathematics used to select a route. The higher the metric associated with
a route, the less desirable it is. For EIGRP, the Bellman-Ford algorithm uses the
following equation and creates the overall 24-bit metric assigned to a route:
* metric = [(K1 × bandwidth) + [(K2 × bandwidth) ÷ (256 - load)] + (K3 × delay)] × [K5÷ (reliability + K4)]
The elements in this equation are as follows:
* By default, K1 = K3 = 1, K2 = K4 = K5 = 0. Therefore, by default, the metric formula
reduces to:
metric = (1 × bandwidth) + (1 × delay)
metric = bandwidth + delay

QUESTION 14:
The Certkiller network is using EIGRP as the network routing protocol. Which of
the following statements correctly describe features and characteristics of routing
using EIGRP? (Select three)
A. It sends periodic updates every 60 seconds.
B. EIGRP uses DUAL to achieve rapid convergence.
C. Adjacencies exist between master routers (MRs) in each domain.
D. It uses multicast to discover other EIGRP routers on an internetwork.
E. EIGRP provides support for multiple network layer protocols: IPX, AppleTalk, and IP.
Answer: B, D, E
Explanation:

B: Enhanced IGRP uses the Diffusing Update based algorithm (DUAL).
D: EIGRP use hello multicast packets for neighbor discovery/recovery.
E: EIGRP supports IPX, Appletalk, and IP. Separate EIGRP instances can be created for
each routed protocol.
Incorrect Answers:
A: EIGRP use triggered updates, not periodic updates.
C: Each EIGRP router maintains a neighbor table that lists adjacent routers. However,
there is no concept of master routers in EIGRP.
Reference: "Introduction to Enhanced IGRP (EIGRP)" Cisco website

QUESTION 15:
While comparing the tables associated with EIGRP and OSPF,
you notice some similarities. Which EIGRP table is similar to OSPF's Link State
Adjacency table?
A. Neighbor table
B. Routing table
C. Topology table
D. Successor table
E. None of the above
Answer: A

Explanation:
Each EIGRP router maintains a neighbor table that lists adjacent routers. This table is
comparable to the neighbors (adjacency) database used by OSPF.
Incorrect Answers:
B: The routing table of EIGRP would compare to the routing table of OSPF
C: Both EIGRP and OSPF contain topology tables, which would compare to each other.
D: EIGRP does not have a successor table. Successors are maintained in the routing and
topology tables of EIGRP.
Reference: Building Scalable Cisco Networks (Cisco Press) page 250


QUESTION 16:
DRAG DROP
Match the correct EIGRP term on the left to the slot in the middle that is adjacent
to the correct description on the right



Answer:
Explanation:
Neighbor table - lists adjacent routers
Topology Table - route entries for all destinations.
Successor - primary route used to reach a destination
Routing table - best routes to a destination
Feasible successor - backup route to the destination.
Explanation:
* Neighbor Table - Each EIGRP router maintains a neighbor table that lists adjacent
routers. This table is comparable to the neighbors (adjacency) database used by OSPF.
* Topology Table - An EIGRP router maintains a topology table for each network
protocol configured: IP, IPX, and AppleTalk. All learned routes to a destination are
maintained in the topology table.
* Routing Table - EIGRP choose the best routes to a destination from the topology table
and places these routes in the routing table. The router maintains one routing table for
each network protocol.
* Successor - This is the primary route used to reach a destination. Successors are kept in
the routing table.
* Feasible Successor - This is a neighbor that is downstream with respect to the
destination, but it is not the least-cost path and thus is not used for forwarding data. In other words, this is a backup route to the destination. These routes are selected at the same time as successors, but are kept in the topology table.
Reference: Building Scalable Cisco Networks (Cisco Press) page 250

QUESTION 17:
Different types of EIGRP transmissions are sent between neighboring routers.
Which three of the following terms are known as 'reliable packets' in EIGRP?
(Select three)
A. Hello
B. ACK
C. Reply
D. Query
E. Update
Answer: C, D, E
Explanation:
Updates are used to convey the reachability of destinations. When a new neighbor is
discovered, update packets are sent so the neighbor can build up its topology table. In this
case, update packets are unicast. In other cases, such as a link cost change, updates are
multicast. Updates are always transmitted reliably.
Queries and replies are sent when destinations go into Active state. Queries are always
multicast unless they are sent in response to a received query. In this case, it is unicast
back to the successor that originated the query. Replies are always sent in response to
queries to indicate to the originator that it does not need to go into Active state because it
has feasible successors. Replies are unicast to the originator of the query. Both queries
and replies are transmitted reliably.
EIGRP reliable packets are: Update, Query and Reply.
EIGRP unreliable packets are: Hello and Ack.
Incorrect Answers:
A, B: Hellos are multicast for neighbor discovery/recovery. They do not require
acknowledgment. A hello with no data is also used as an acknowledgment (ack). Acks
are always sent using a unicast address and contain a non-zero acknowledgment number.
Reference: Cisco BSCN version 1.0 study guide, pages 6-18.
QUESTION 18:
Which one of the following statements best describes the way EIGRP advertises
subnet mask information to its destination networks?
A. EIGRP advertises a prefix length for each destination network.
B. EIGRP advertises a fixed length subnet mask for each destination network.
C. EIGRP advertises only a classful subnet mask for each destination network.
D. EIGRP, like IGRP and RIP, does not advertise a subnet mask for each destination
network.
Answer: A

Explanation:

EIGRP advertises a prefix length to each destination network. It supports VLSM which
allows subnet masks to be automatically summarized at the network boundary, and
EIGRP can also be configured to summarize on any bit boundary at any interface.
Incorrect Answers:
B: This is incorrect because EIGRP supports Variable Length subnet masks.
C: This is incorrect because EIGRP is considered to be a classless protocol, not classful.
D: EIGRP is more sophisticated then IGRP and RIP and actually does advertise a subnet
mask to each destination network.
QUESTION 19:
EIGRP was designed specifically not to use excessive bandwidth for routing updates
and functions across WAN links. If EIGRP is configured on an interface, what is the
maximum percent of its bandwidth EIGRP would use, by default?
A. 10%
B. 25%
C. 50%
D. 75%
E. 100%
Answer: C
Explanation:

By default, EIGRP will limit itself to using no more than 50% of the available
bandwidth. The maximum bandwidth that can be used is a configurable parameter.
Reference: Cisco, Configuration Notes for the Enhanced Implementation of EIGRP.
http://www.cisco.com/warp/public/103/12.html
QUESTION 20:
EIGRP supports Variable Length Subnet Masking (VLSM). Which two features of
EGIRP are true regarding EIGRP support for VLSM? (Select two)
A. It advertises a routing mask
B. It is a classful routing protocol
C. It is a classless routing protocol
D. It does not advertise a routing mask.
Answer: A, C
Explanation:
EIGRP includes the routing mask when it advertises routes. Subnet mask information
must be included in all routing updates for classless protocols. EIGRP is a classlessprotocol, meaning that is does not solely rely on the network class in order to find the
subnet mask. These two features enable EIGRP to support VLSM.
Incorrect Answers
B: Classful routing protocols do not support VLSM.
D: The subnet mask must be included in the route to support VLSM.

QUESTION 21:
In an effort to decrease the size of the routing tables in the Certkiller network,
summarization is being configured on all routers. Where in an EIGRP network is it
most appropriate to implement route summarization?
A. At area border routers
B. At autonomous system boundary routers
C. It is done automatically by the DR router in each area
D. Manually at any interface of any EIGRP router within the network
E. In backbone area routers.
Answer: B
Explanation:

Enhanced IGRP performs route summarization at classful network boundaries by default.
Automatic route summarization occurs at major network boundaries. ASBRs
(autonomous system boundary routers) are used at the major network boundaries.
Incorrect Answers
A, C, E: Area Border Router and DR are used in OSPF, but not in EIGRP. Backbone area
routers are also concepts used in OSPF, but not in EIGRP.
D: Manual summarization can be done in any interface at any router within network, but
this is not the preferred solution. Summarizing manually at each router can result in black
hole routing. However, done properly this is an acceptable practice. If the question calls
for more than one answer then the best choice would be B and D.

QUESTION 22:
The Certkiller network is using route summarization to decrease the size of the
routing tables. In an EIGRP network, which of the following describes the best
method for implementing summarization?
A. At WAN interfaces.
B. Manually at major network boundaries.
C. Dynamically at discontiguous interfaces.
D. Dynamically at major network boundaries.
Answer: D
Explanation:

EIGRP supports arbitrary route summarization. Route summarization takes place
automatically at major network boundaries (where network are supernetted).
Note: Route summarization is the consolidation of advertised addresses.
Incorrect Answers
A: Manually configuring summarization at WAN boundaries is not necessarily
recommended in all situations. If the routers belong to the same major network boundary
then summarization should not be configured.
B: Route summarization is automatic in EIGRP, and it is recommended to keep the
defaults.
C: Route summarization should only be applied at contiguous interfaces. Choosing this
option would most likely lead to black hole routing, making many networks unreachable.

QUESTION 23:
The Certkiller network is running EIGRP on the T1 links within their NBMA frame
relay network. By default what would the hold time be for hello packets across these
WAN links?
A. 30 seconds
B. 60 seconds
C. 90 seconds
D. 180 seconds
E. 5 Seconds
Answer: D
Explanation:

EIGRP sends hello packets every 5 seconds on high bandwidth links and every 60
seconds on low bandwidth multipoint links. The hold time is typically three times the
hello interval. In this scenario, on slow NBMA media, hold time will be 180 seconds.
Incorrect Answers:
A, B, C: Although the hello timers can be manually configured for these values, they are
not the default time.
E: This is the default for high bandwidth links, such as Ethernet networks.
Reference: Enhanced Interior Gateway Routing Protocol
http://www.cisco.com/warp/public/103/eigrp1.html

QUESTION 24:
EIGRP is being used as the routing protocol within the Certkiller network. Which
two of the following features allow EIGRP to support classless routing? (Select two)
A. Djikstra's algorithm
B. discontiguous subnets
C. variable length subnet masks
D. periodic update announcements
E. unequal path-cost load balancing
Answer: B, C
Explanation:


B: Discontiguous subnets are supported by EIGRP. This is a classless routing protocol
feature.
C: EIGRP support variable length subnet masks (VLSM). This is a classless routing
protocol feature.
Incorrect Answers
A: EIGRP use the DUAL algorithm, not the Djikstra's algorithm. The Djikstra algorithm
is used by distance vector protocols. EIGRP is considered to be a hybrid routing protocol.
D: EIGRP use periodic hello messages, not update announcements. EIGRP use update
packets to convey reachability of destinations. When a new neighbor is discovered,
Update packets are sent so the neighbor can build up its. These are not periodic, however.
E: IGRP and EIGRP support unequal cost path load balancing, which is known as
variance. However, this is not a classless feature of EIGRP.
Note: Classless routing protocols include the routing mask with the route advertisement.
This enables discontiguous subnets and variable length subnet masks.
Reference: Introduction to Enhanced IGRP (EIGRP)
http://www.cisco.com/warp/public/103/1.html
How Does Unequal Cost Path Load Balancing (Variance) Work in IGRP and EIGRP?
http://www.cisco.com/warp/public/103/19.html

QUESTION 25:
EIGRP is being used as the routing protocol on the Certkiller network. While
troubleshooting some network connectivity issues, you notice a large number of
EIGRP SIA (Stuck In Active) messages. What causes these SIA routes? (Select two)
A. The neighboring router stops receiving ACK packets from this router.
B. The neighboring router starts receiving route updates from this router.
C. The neighboring router is too busy to answer the query (generally caused by high CPU
utilization).
D. The neighboring router is having memory problems and cannot allocate the memory
to process the query or build the reply packet.
Answer: C, D
Explanation:
SIA routes are due to the fact that reply packets are not received. This could be caused by
a router which is unable to send reply packets. The router could have reached the limit of
its capacity, or it could be malfunctioning.
Incorrect Answers
A: Missing replies, not missing ACKs, cause SIA.
B: Routes updates do not cause SIA
Notes: If a router does not receive a reply to all outstanding queries within 3 minutes, the
route goes to the stuck in active (SIA) state. The router then resets the neighbors that fail
to reply by going active on all routes known through that neighbor, and it re-advertises
all routes to that neighbor.
Reference: Enhanced Interior Gateway Routing Protocol
http://www.cisco.com/warp/public/103/eigrp3.html

Share this

Related Posts

There was an error in this gadget