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Building Cisco Multilayer Switched
Networks (BCMSN)
Exam 642-811 Edition 2.0

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Q1. Which feature will put a switch port into the error-disabled state upon receipt of Spanning Tree
data messages, requiring a network administrator to manually put the port back in service?

A. Loop Guard
B. Port Fast
C. BDPU Guard
D. Root Guard
E. BDPU Filtering

Answer: C


Reference: Building Cisco Multilayer Switched Networks (Ciscopress) page 412
Q3. Which are two closely related standards specifically designed for data transmission over fiber
optic networks? (Choose two.)

A. FDDI
B. SONET
C. SDH
D. DSL
E. ATM
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Answer: B, E

Explanation: Synchronous Digital Hierarchy. The European standard that defines a rate and format
for transmission of optical signals over fiber using ATM and SONET. In contrast to PDH, SDH
provides for a synchronous multiplexing scheme.

Reference:
http://www.cisco.com/en/US/products/hw/optical/ps2011/prod_technical_reference09186a00800a
8655.html#998751

C. Multicast Open Shortest Path First (MOSPF)
D. Protocol Independent Multicast Sparse Mode (PIM-SM)
E. Core-Based Trees (CBT)

Answer: D

Explanation: Multicast routing protocols fall into two categories: Dense-mode (DM) and Sparse-
mode (SM). DM protocols assume that almost all routers in the network will need to distribute
multicast traffic for each multicast group (for example, almost all hosts on the network belong to
each multicast group). Accordingly, DM protocols build distribution trees by initially flooding the
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entire network and then pruning back the small number of paths without receivers. SM protocols
assume that relatively few routers in the network will be involved in each multicast. The hosts
belonging to the group are widely dispersed, as might be the case for most multicasts in the
Internet. Therefore, SM protocols begin with an empty distribution tree and add branches only as
the result of explicit requests to join the distribution.

Reference:
http://www.cisco.com/en/US/tech/tk828/tk363/technologies_white_paper09186a0080092942.sht
ml
Q6. Drag and drop the type of flow mask used with Multiplayer Switching (MLS) in the options
column to the statement that defines its character in the target column.
D. CBWFQ

Answer: B

Explanation: With class-based QoS queuing, you can create up to 64 classes for an interface.
(Unlike WFQ, queues are not automatically based on the packet's ToS value.) Class-based QoS
queuing also lets you control the drop mechanism used when congestion occurs on the interface.
You can use WRED for the drop mechanism, and configure the WRED queues, to ensure that high-
priority packets within a class are given the appropriate weight. If you use tail drop, all packets
within a class are treated equally, even if the ToS values are not equal.

Reference:
http://www.cisco.com/en/US/products/sw/cscowork/ps2064/products_user_guide_chapter09186a0
0800e0a04.html
Q8. Which technology manages multicast traffic at Layer 2 by configuring Layer 2 LAN interfaces
dynamically to forward multicast only to those interfaces that want to receive it?

A. IGMP
B. IGMP snooping
C. PIM-DIM
D. DVMRP
E. MOSPF

Answer: B

Explanation:
Understanding IGMP Snooping


Port VLANs in spanning tree forwarding state and not pruned
fa0/1 1-6, 8-100, 102-105, 108-999, 1002-1005

The network operations center has received a call stating that users in VLAN 107 are unable to
access resources through Router Router1.

From this information contained in the graphic, what is the cause of this problem?

A. VLAN 107 does not exist on switch SwitchA.
B. VTP is pruning VLAN 107.
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C. VLAN 107 is not configured on the trunk.
D. Spanning tree is not enabled on VLAN 107.

Answer: D Q10. Which two table types are CEF components? (Choose two.)

A. Forwarding information base
B. Adjacency tables
C. Neighbor tables
D. Caching tables
E. Route tables

Answer: A, B
Q12. As a design rule, what is the maximum time that should be allowed for a voice packet to
cross a network?

A. 60 milliseconds
B. 120 milliseconds
C. 150 milliseconds
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D. 210 milliseconds

Answer: C

Explanation: Delay is the time it takes for VoIP packets to travel between two endpoints and you
should design networks to minimize this delay. However, because of the speed of network links and
the processing power of intermediate devices, some delay is expected. The human ear normally
accepts up to about 150 milliseconds (ms) of delay without noticing problems (the ITU's G.114
standard recommends no more than 150 ms of one-way delay).

Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5014/products_feature_guide09186a008008
80e7.html
Q13. What information do CGMP-enabled switches and routers exchange using the CGMP protocol?


Reference:
http://www.cisco.com/en/US/tech/tk583/tk547/technologies_tech_note09186a0080094e99.shtml
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Q15. What are three possible router states of HSRP routers on an LAN? (Choose three.)

A. Standby
B. Established
C. Active
D. Idle
E. Backup
F. Init

Answer: A, C, F

Explanation: Using HSRP, a set of routers works in concert to present the illusion of a single virtual
router to the hosts on the LAN. This set is known as an HSRP group or a standby group. A single
router elected from the group is responsible for forwarding the packets that hosts send to the
virtual router. This router is known as the Active router. Another router is elected as the Standby
router. In the event that the Active router fails, the Standby assumes the packet-forwarding duties
of the Active router. Although an arbitrary number of routers may run HSRP, only the Active router
forwards the packets sent to the virtual router.

Reference:
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml

described by two VLAN numbers, the lesser one first, separated by a hyphen.

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Reference:
http://www.cisco.com/en/US/products/hw/switches/ps663/products_command_reference_chapter
09186a0080144e79.html#1022676
Q17. In a Cisco switch with redundant power supplies of the same wattage, how is the total power
available to the switch provided when both supplies are operating normally? (Choose two.)

A. Total combined power of both supplies.
B. Total power of one supply.
C. Total power required is shared nearly equally by both supplies.
D. Total power is the sum of one-half of total power of both supplies.

Answer: C, D

Explanation: Specifying the redundant keyword enables redundancy. In a redundant configuration,
the total power drawn from both supplies is at no time greater than the capability of one supply. If
one supply malfunctions, the other supply can take over the entire system load. When you install
and turn on two power supplies, each
concurrently provides approximately half of the required power to the system. Load sharing and
redundancy are enabled automatically; no software configuration is required.

Reference:

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A. Managed remote access
B. Password protection
C. Security surveillance
D. Privilege levels
E. Physical security
F. Inventory audit

Answer: A, B, D, E

Explanation: The policy to control access to network devices should be one of the first components
of the access policy. All devices at every layer of the campus network should have a plan to provide
for the following:
• Physical security
• Passwords
• Privilege levels to allow limited access to a network device
• Limiting virtual terminal or telnet access

Reference: Building Cisco Multilayer Switched Networks (Ciscopress) page 368
Q20. How does a non-Root switch choose its Root Port?

A. It chooses the port with the lowest cumulative Root Path Cost to the Root Bridge.
B. It chooses the port with the highest cumulative Root Path Cost to the Root Bridge.
C. The port receives an inferior BPDU from a neighboring switch on a shard LAN segment.
D. The port receives a BPDU announcing a higher Root Path Cost from a neighboring switch on a

information needed to switch the packet to the next hop. This Layer 2 information is generally
contained in the ARP cache table. Cisco Express Forwarding creates a adjacency table to prepend
the layer 2 information.

Reference: Building Cisco Multilayer Switched Networks (Ciscopress) page 412
Q22. In the hardware address 0000.0c07.ac0a what does 07.ac represent?

A. Vendor code
B. HSRP group number
C. HSRP router number
D. HSRP well-known physical MAC address
E. HSRP well-known virtual MAC address

Answer: E

Explanation: HSRP code (HSRP well-known virtual MAC address) – The fact that the MAC address is
for an HSRP virtual router is indicated in the next two bytes of the address. The HSRP code is
always 07.ac.

Reference: Building Cisco Multilayer Switched Networks (Ciscopress) page 268
Q23. IEEE 802.1w RSTP defines which port states?

A. Listening, Learning, Forwarding, Blocking, Disabled
B. Learning, Forwarding, Discarding