Braindumps for "642-521" Exam

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Question 1.
What is the significance of the number 128 in the fair-queue 128 router command?

A. It is the priority value for the interface.
B. It is the minimum bandwidth level for the queue.
C. It is the maximum bandwidth allocation for the queue.
D. It is the number of queues that will be allocated from memory.
E. It is the maximum number of messages that will be queued for a traffic type.

Answer: E

Explanation:
fair-queue (WFQ)
To enable weighted fair queueing (WFQ) for an interface, use the fair-queue interface configuration command. 

To disable weighted fair queueing for an interface, use the no form of this command.
fair-queue [congestive-discard-threshold [dynamic-queues [reservable-queues]]] no fair-queue

Syntax Description
 

fair-queue (class-default)
To specify the number of dynamic queues to be reserved for use by the class-default class as part of the default class policy, use the fair-queue policy-map class configuration command. 

To delete the configured number of dynamic queues from the class-default policy, use the no form of this command.
fair-queue [number-of-dynamic-queues]
no fair-queue [number-of-dynamic-queues]

Syntax Description

 

Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_command_reference_chapter09186a0080080794.html#72940 

Question 2.
Which two traffic queuing methods are enabled by default on Cisco routers? (Choose two)

A. FIFO
B. Priority
C. Custom
D. Weighted Fair

Answer: A, D

Question 3.
Which commands displays information on multilink bundles that are active?

A. show multilink
B. show ppp status
C. show mlppp status
D. show ppp multilink
E. show ppp negotiation

Answer: D

Explanation:
show ppp multilink
To display bundle information for the Multilink PPP bundles, use the show ppp multilink command in EXEC mode.
show ppp multilink
Syntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History

 

Examples
The following is the output when no bundles are on a system:
Router# show ppp multilink
No active bundles
The following is the output when a single Multilink PPP bundle (named rudder) is on a system:
Router# show ppp multilink B
undle rudder, 3 members, first link is BRI0: B-channel 1
0 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sent
The following is the output when two active bundles are on a system. Subsequent bundles would be displayed below the previous bundle.
Router# show ppp multilink
Bundle rudder, 3 members, first link is BRI0: B-Channel 1
0 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sent
Bundle dallas, 4 members, first link is BRI2: B-Channel 1
0 lost fragments, 28 reordered, 0 unassigned, sequence 0x12E/0x12E rcvd/sent

 
 

Question 4.
Multilink PPP can improve throughput and reduce latency by using which two features?
(Choose two)

A. Adding 8 kbps to each B channel for 16 kbps in-band management.
B. Load balancing based on an XOR of the Layer 2 addresses in the packets.
C. Bandwidth aggregation by splitting packets and sending the fragments over parallel circuits.
D. Initializing the second B channel when the first B channel reaches a specified bandwidth  
    utilization.

Answer: C, D

Question 5.
What is the EIGRP multicast flow timer?

A. The timer after which EIGRP stops forwarding multicast data traffic.
B. The timeout timer after which EIGRP retransmits, unicasting the neighbor not in CR mode.
C. The time interval between consecutive received EIGRP hello intervals.
D. The time interval between consecutive transmitted EIGRP hello intervals.
E. The timeout timer after which EIGRP retransmits, unicasting the neighbor in CR mode.

Answer: B

Table 49 show ip eigrp interfaces Field Descriptions
Field Description
Interface Interface over which EIGRP is configured.
Peers Number of directly connected EIGRP neighbors.
Xmit Queue Number of packets remaining in the Unreliable and Reliable transmit queues.
Un/Reliable
Mean SRTT Mean smooth round-trip time (SRTT) interval (in seconds).
Pacing Time Pacing time used to determine when EIGRP packets should be sent out the
Un/Reliable interface (unreliable and reliable packets).
Multicast Flow Maximum number of seconds in which the router will send multicast Timer EIGRP packets.
Pending Routes Number of routes in the packets in the transmit queue waiting to be sent.

Reference:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_command_reference_chapter09186a00801a80d7.html 

Question 6.
What is NOT a BGP attribute?

A. Origin
B. Weight
C. Local_pref
D. Community
E. Cluster_list

Answer: E

Reference:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/bgp.htm  

Question 7.
Which BGP attribute are "well known"?

A. Next-hop
B. Aggregator
C. AS-path
D. Atomic-aggregate
E. MED

Answer: A, C, E

Reference:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/bgp.htm 

Question 8.
With which two Cisco IOS Firewall security features is the authentication proxy compatible? (Choose two)

A. Cisco router
B. NAT
C. PAT
D. CBAC
E. RADIUS
F. TACACS+

Answer: B, D

Question 9.
What does a half-open TCP session on the Cisco IOS Firewall mean?

A. Session was denied.
B. Firewall detected return traffic.
C. Session has not reached the established state.
D. Three-way handshake has been completed.

Answer: C

Question 10.
What does CBAC on the Cisco IOS Firewall do with the application-layer protocol session information it gets from TCP and UDP packets?

A. Creates temporary openings in the firewall's ACLs to allow return traffic and additional data 
     connections for permissible sessions.
B. Provides additional visibility at intranet, extranet, and Internet perimeters.
C. Protects the network from internal and external attacks and threats.
D. Creates specific security polices for each user.

Answer: A

Question 11.
How many VLANs can a single RSM support?

A. 1
B. 16
C. 256
D. 1024

Answer: C

Explanation:
The RSM supports interVLAN routing for up to 256 VLANs.

Reference:
http://www.cisco.com/en/US/products/hw/switches/ps679/products_configuration_guide_chapter09186a008007e802.html 

Question 12.
You enter the set ip route command to configure a default route in which platform?

A. Catalyst 2900XL
B. Catalyst 3500XL
C. Catalyst 5000
D. Catalyst 12000

Answer: C

Explanation:
The switch sends all off-network IP traffic to the primary default gateway. If connectivity to the primary gateway is lost, the switch attempts to use the backup gateways in the order they were configured. The switch sends periodic ping messages to determine whether each default gateway is up or down. If connectivity to the primary gateway is restored, the switch resumes sending traffic to the primary.

To specify one or more default gateways, perform this task in privileged mode:
 
 

This example shows how to configure three default gateways on the switch and how to verify the default gateway configuration:
Console> (enable) set ip route default 10.1.1.10
Route added.
Console> (enable) set ip route default 10.1.1.20
Route added.
Console> (enable) set ip route default 10.1.1.1 primary
Route added.
Console> (enable)
Console> (enable) show ip route
Fragmentation Redirect Unreachable
------------- -------- -----------
enabled enabled enabled
The primary gateway: 10.1.1.1
Destination Gateway RouteMask Flags Use Interface
--------------- --------------- ---------- ----- -------- ---------
default 10.1.1.1 0x0 UG 6 sc0
default 10.1.1.20 0x0 G 0 sc0
default 10.1.1.10 0x0 G 0 sc0
10.0.0.0 10.1.1.100 0xff000000 U 75 sc0
default default 0xff000000 UH 0 sl0
Console> (enable)

Reference:
http://www.cisco.com/en/US/products/hw/switches/ps679/products_configuration_guide_chapter09186a008007f7b6.htm 

Question 13.
What are three valid combinations of trunk modes for ports configured as link partners? 
(Choose three)

A. On/On
B. On/Auto
C. Auto/Auto
D. Desirable/Auto
E. Nonegotiate/Desirable

Answer: A, B, D

Explanation:
You can configure a port with any one of these modes for each protocol group: on, off, or auto. If the configuration is set to on, the port receives all the flood traffic for that protocol. If the configuration is set to off, the port does not receive any flood traffic for that protocol.

If the configuration is set to auto, a port becomes a member of the protocol group only after the device connected to the port transmits packets of the specific protocol group. The switch detects the traffic, adds the port to the protocol group, and begins forwarding flood traffic for that protocol group to that port. Autoconfigured ports are removed from the protocol group if the attached device does not transmit packets for that protocol within 60 minutes. Ports are also removed from the protocol group when the supervisor engine detects that the link is down on the port.

The Port Aggregation Protocol (PAgP) facilitates the automatic creation of EtherChannels by exchanging packets between Ethernet ports. PAgP packets are exchanged only between ports in auto and desirable modes. 

Ports configured in on or off mode do not exchange PAgP packets. The protocol learns the capabilities of port groups dynamically and informs the other ports. After PAgP identifies correctly matched EtherChannel links, it groups the ports into an EtherChannel. The EtherChannel is then added to the spanning tree as a single bridge port. 

EtherChannel includes four user-configurable modes: on, off, auto, and desirable. Only auto and desirable are PAgP modes. You can modify the auto and desirable modes with the silent and non-silent keywords. By default, ports are in auto silent mode.

Table 6-1 describes EtherChannel modes.

 

Both the auto and desirable modes allow ports to negotiate with connected ports to determine if they can form an EtherChannel, based on criteria such as port speed, trunking state, and VLAN numbers.
Ports can form an EtherChannel when they are in different PAgP modes as long as the modes are compatible:
• A port in desirable mode can form an EtherChannel successfully with another port that is in desirable or auto mode.
• A port in auto mode can form an EtherChannel with another port in desirable mode.
• A port in auto mode cannot form an EtherChannel with another port that is also in auto mode, because neither port will initiate negotiation.

Reference:
http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a008007fb26.html 

Question 14.
You must configure an Ethernet trunk between two Cisco switches.

Which three statements about the trunk link are true? (Choose three)

A. The link may be 100 Mbps or faster.
B. The link may use ISL and be point-to-point.
C. The link may use the 802.1Q trunk protocol and be point-to-point.
D. The link may use the 802.10 trunk protocol, providing the SAID parameter is correctly set.

Answer: A, B, C

Explanation:
Trunks are used to carry traffic belonging to multiple VLANs between devices over the same link. A device can determine which VLAN the traffic belongs to by its VLAN identifier. The VLAN identidfier is a tag that is encapsulated with the data. ISL and 802.1q are two types of encapsulations used to carry data from multiple VLANs over trunk links.

ISL is a Cisco proprietary protocol for interconnecting multiple switches and maintaining VLAN information as traffic goes between switches. ISL provides VLAN trunking capabilities while maintaining full wire speed performance on Ethernet links in full646 duplex or half-duplex mode. ISL operates in a point-to-point environment and will support up to 1000 VLANs. In ISL, the original frame is encapsulated and an additional header is added before the frame is carried over a trunk link. At the receiving end, the header is removed and the frame is forwarded to the assigned VLAN. .ISL uses Per VLAN Spanning Tree(PVST) which runs one instance of Spanning Tree Protocol (STP) per VLAN. PVST allows to optimize root switch placement for each VLAN and supports load balancing of VLANs over multiple trunk links.

802.1Q is the IEEE standard for tagging frames on a trunk and supports upto 4096 VLANs. In 802.1Q, the trunking device inserts a four-byte tag into the original frame and recomputes the Frame Check Sequence (FCS) before sending the frame over the trunk link. 

At the receiving end, the tag is removed and the frame is forwarded to the assigned VLAN.

802.1Q does not tag frames on the native VLAN. It tags all other frames transmitted and received on the trunk. While configuring 802.1 trunk, you must make sure that the same native VLAN is configured on both sides of the trunk. IEEE 802.1Q defines a single instance of spanning tree running on the native VLAN for all the VLANs in the network which is called Mono Spanning Tree (MST). This lacks the flexibility and load balancing capability of PVST available with ISL. However, PVST+ offers the capability to retain multiple Spanning Tree topologies with 802.1Q trunking.

Reference:
http://www.cisco.com/en/US/tech/CK389/CK390/technologies_tech_note09186a0080094665.shtml  

Question 15.
Which command do you use to check the trunking mode on Catalyst 3500XL switches?

A. show trunk
B. show vtp mode
C. show interface
D. show interface switchport

Answer: D

Question 16.
What are two functions of VTP? (Choose two)

A. It propagates global VLAN information.
B. It maps mixed-media to Ethernet VLANs.
C. It sets trunk priority levels of adjacent switches.
D. It adjusts VLAN interswitch links for parallel load sharing.
E. It maps the noncontiguous switch fabric across the global VLAN.

Answer: A, B

Question 17.
You are configuring a VLAN trunk on Fast Ethernet.
Which two trunking modes negotiate correctly when brining up a trunk link? (Choose two)

A. Off
B. Auto
C. Negotiate
D. Desirable
E. Nonegotiate

Answer: B, D

Question 18.
What are two methods to maintain a consistent VLAN database in a VTP domain?
(Choose two)

A. Do not configure any switches as a VTP server.
B. Ensure that all switches not authorized to make changes are in Client mode.
C. Always configure switches using VTP server mode when adding them to the existing network.
D. Allow only one VTP server in each domain so that adding and deleting VLANs can be 
     centralized to one location.

Answer: B, D

Question 19.
Which three actions configure multilayer switching on the multilayer switching route processor? (Choose three)

A. Enabling MLSP
B. Setting the MLS aging time
C. Including an external MLS-RP
D. Assigning a VLAN ID to an interface
E. Configuring the MLS management interface

Answer: A, D, E

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