2013 Latest Cisco 350-001 Exam Section 2: LAN Switching (21

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2013 Latest Cisco 350-001 Exam Section 2: LAN Switching (21 Questions)

QUESTION NO: 1
You are having connectivity problems with the network shown below: Router TK2 is able to ping the Catalyst switch TK3, but router TK1 cannot.
What is the probable cause of this problem?
A. There is no VTP domain on the Catalyst switch.
B. The incorrect VLAN is attached to the command interface of the Catalyst.
C. There is no default route configured on the switch.
D. An incorrect IP address on the switch.
E. ICMP packets are being filtered on the switch TK3
Answer: C
Explanation:
Without a default route on Cat TK3, TK3 will not know how to get packets back to TK1. Catalyst TK3 would be able to ping router TK2 without a default route, however, because they share the same IP subnet.
Incorrect Answers:
A, B. VTP and VLAN information that is configured incorrectly could explain problems associated with local LAN users attached to the TK3, but this would not explain why TK1 would not be able to reach TK3.
D. If TK3 had an incorrect IP address, then TK2 would not be able to ping TK3.
E. If all ICMP packets were filtered, then TK2 would also not be able to ping TK3. This answer could be the problem only if ICMP were being filtered from router TK1.

QUESTION NO: 2 What is the Cisco recommended best practice PaGP setting for ports Etherchannel trunks?
A. on – on

B. auto – auto
C. desirable – on
D. desirable – auto
E. desirable – desirable
Answer: E

Explanation:
Using PAgP to Configure EtherChannel (Recommended)

PAgP facilitates the automatic creation of EtherChannel links by exchanging packets between channel-capable ports. The protocol learns the capabilities of port groups dynamically and informs the neighboring ports. After PAgP identifies correctly paired channel-capable links, it groups the ports into a channel. The channel is then added to the spanning tree as a single bridge port. A given outbound broadcast or multicast packet is transmitted out one port in the channel only, not out every port in the channel. In addition, outbound broadcast and multicast packets transmitted on one port in a channel are blocked from returning on any other port of the channel. There are four user-configurable channel modes: on, off, auto, and desirable. PAgP packets are exchanged only between ports in auto and desirable mode. Ports configured in on or off mode do not exchange PAgP packets. For switches to which you want to form an EtherChannel, it is best to have both switches set to desirable mode. This gives the most robust behavior if one side or the other encounters error situations or is reset. The default mode of the channel is auto. Both the auto and desirable modes allow ports to negotiate with connected ports to determine if they can form a channel. The determination is based on criteria such as port speed, trunking state, and native VLAN. Ports can form an EtherChannel when they are in different channel modes as long as the modes are compatible. This list provides examples:
*
A port in desirable mode can successfully form an EtherChannel 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, since neither port initiates negotiation.

*
A port in on mode can form a channel only with a port in on mode because ports in on
mode do not exchange PAgP packets.

*
A port in off mode cannot form a channel with any port.
Reference:
http://www.cisco.com/en/US/tech/tk389/tk213/technologies_tech_note09186a00800949c2.shtml#pagptoconf

Additional Information:
The Best practices for Cisco Catalyst switch configurations can be found in this document:
http://www.cisco.com/en/US/products/hw/switches/ps700/products_white_paper09186a00801b49a4.shtml
From this Best Practices document: Cisco Configuration Recommendation for L2 ChannelsCisco recommends enabling PAgP and using a setting of desirable-desirable on all EtherChannel links. Refer to the output below for more information: Switch(config)#interface type slot/portSwitch(config-if)#no ip address!— Ensures that there is no IP!— address assigned to the LAN port.Switch(config-if)#channel-group mode desirable!— Specify the channel number and the PAgP mode.Verify the configuration, as shown below. Switch#show run interface port-channel numberSwitch#show running-Config interface type slot/portSwitch#show interfaces type slot/port etherchannelSwitch#show etherchannel port-channel

QUESTION NO: 3
You wish to implement Ethernet Channels in your switched LAN. Which of the following are valid statements that should be kept in mind before this implementation? (Choose all that apply)
A. Ports within a Fast Ether Channel need to have identical duplex and speed settings.
B. Port Aggregation Protocol (PAGP) facilitates the automatic creation of Fast Ether channels links.
C. Ports within a Fast Ether Channel may be assigned to multiple VLANs.
D. Fast Ethernet Channels can not be configured as a trunk.
E. Only Fast Ethernet ports can be channeled.
Answer: A, B
Explanation:
You can not mix and match different types of Ethernet ports, such as 10M, 100M, GIGE,
etc into the same channel. All ports in the channel need to have the same speed settings.
Similarly, all ports need to be configured to have identical duplex settings.
The Port aggregation protocol (PAgP) aids in the automatic creation of Fast EtherChannel
links. PAgP packets are sent between Fast EtherChannel-capable ports in order to
negotiate the forming of a channel.

Incorrect Answers:
C. Ports in the channel can only be assigned to one VLAN.
D. Ethernet channels can indeed be set up as trunks.
E. Ethernet channels can be set up for fast Ethernet, Gigabit Ethernet, and 10 Gigabit Ethernet.

QUESTION NO: 4
A new Catalyst switch is added to the Testking switched LAN. Users attached to the new switch are having connectivity problems. Upon troubleshooting, you realize that the new switch is not dynamically learning any VLAN information via VTP from the other switches. What could be causing this problem?
A. The other switches are different Catalyst models.
B. There are no users on one of the existing switches.
C. The other upstream switches are VTP clients.
D. The VTP domain name is not properly configured.
E. The native VLAN on the trunk is VLAN 1.
Answer: D
Explanation:
In order for VTP information to be propagated throughout the network, every LAN switch participating in the VTP domain must have the exact same VTP domain name configured.
Incorrect Answers:
A. All Catalyst switch models support VTP.
B. The number of users or types of devices attached to any switch has absolutely no bearing on the functionality of VTP.
C. VTP clients can pass updates to each other to propagate VLAN info throughout the network. All VTP client switches do not necessarily need to be directly connected to a VTP server.
E. VLAN 1 is the default VLAN for all Catalyst switches. Although it is not necessarily recommended that all switches use this default VLAN, VTP information would be able to pass throughout the network if they did.

QUESTION NO: 5
The Testking network is implementing a new Layer 3 Switching architecture. When an IP packet is Layer 3-switched from a source in one VLAN to a destination in another VLAN, what field in a packet will be rewritten?
A. Layer 3 destination address
B. Layer 3 source address
C. Layer 2 TTL
D. Layer 3 TTL
E. Layer 3 Transport Protocol
Answer: D
Explanation:
When a packet is Layer 3 switched, the source and destination MAC address, as well as the IP TTL and IP checksum is rewritten.
Layer 2 EthernHeader et Layer 3 IP Header Data FCS
DestinatMAC ion Source MAC DestinatIP ion Source IP TTL Checksu m
ReceivFrame ed Router MAC Address Host-A MAC Address Host-B Host-A n value1
RewrittFrame en Next Hop MAC Address Router MAC Address Host-B Host-A n-1 value2
The Table above displays the details of the received frame that are indicated and then the details required for the rewritten frame that is transmitted after routing are shown. Notice that the following fields must be modified for the rewritten frame that is forwarded to the next hop routing device:
1. Destination MAC address:
The MAC address of the next hop must be written to the
rewritten frame.
2.
Source MAC address: The source MAC address must be written to the MAC address of the router.
3.
IP TTL: This must be decremented by one, as per the normal rules of IP routing.
4.
IP Header Checksum: This must be recalculated, as the TTL field changes.
The process of how the data plane operations shown in Table 6-1 are implemented is where the difference between a traditional router and Layer 3 switch lie. A traditional router uses the same general purpose CPU used to perform control plane operations to also implement data plane operations, meaning data plane operations are handled in software. A Layer 3 switch on the other hand uses an ASIC to perform data plane operations because it is very easy to program the very simple operations required for the data plane into an ASIC. In this respect, the data plane is implemented in hardware because a series of hardware operations are programmed into the ASIC that perform the data plane operations required for routing a packet. Reference: Justin Menga, CCNP Practical Studies: Layer 3 switching.

QUESTION NO: 6 By default, which of the following VLANs are eligible for pruning in a Catalyst 6509 switch? (Choose all that apply)
A. VLAN 1
B. VLAN 2
C. VLAN 999
D. VLAN 1000
E. VLAN 1001
F. VLAN 4094
Answer: B, C, D
Explanation:
By default, VLANs 2-1000 are pruning eligible in a Catalyst switch. For the default VLAN settings in Catalyst switches see the following document: http://www.cisco.com/en/US/partner/products/hw/switches/ps708/products_configuration_guide_chapter09186a

QUESTION NO: 7 You have ISL trunks configured between two Catalyst switches, and you wish to load share traffic between them. Which method of load sharing can you utilize?
A. Load sharing of traffic over parallel ISL trunks on a per flow basis.
B. Load sharing of traffic over parallel ISL trunks on a per VLAN basis.
C. Load sharing of traffic over parallel ISL trunks on a per packet basis.
D. Automatic round robin load sharing of VLAN traffic.
Answer: B
Explanation:
It is possible to load share over parallel ISL trunks on a per-VLAN basis, using either path costs or port priorities, or a combination of these two methods. However, this will only load share traffic from different VLANs, and not evenly distribute traffic from the same VLAN as the STP process will only allow a single VLAN to use one of the ISL trunks.
Incorrect Answers:
A, C. It is not possible to load share on a per flow or per packet basis as any given VLAN will only traverse over one of the ISL trunks. The other trunk will be in a blocking state for that particular VLAN.
D. Automatic load sharing is not possible over parallel ISL trunks.

QUESTION NO: 8
You are trying to bring up an ISL trunk link between two switches. The trunk mode on the local end is set to auto. However, the ISL trunk never comes up.
What is the probable cause of this problem? (Choose all that apply.)
A. The trunk mode on the remote end is set to on.
B. The trunk mode on the remote end is set to off.
C. The trunk mode on the remote end is set to auto.
D. The trunk mode on the remote end is set to desirable.
E. The trunk mode on the remote end is set to nonegotiate.
Answer: B, C, E
Explanation:
The trunk mode can be: auto, Desirable, On, nonegotiate, and Off. When set to “off” ISL is not allowed on this port regardless of the mode configured on the other end. When set to “auto” the port listens for Dynamic Trunking Protocol (DTP) frames from the remote
the remote device to make the trunking decision. Thus, if both ends are set to Auto, no trunking will occur. When set to nonegotiate, DTP is not spoken to the neighboring switch. nonegotiate automatically enables ISL trunking on its port, regardless of the state of its neighboring switch. However, according to Cisco when one end is set to auto, and the other end is set to nonegotiate, then the result is a non-trunking port (see the table at the middle of the Cisco link, used as a reference).
Incorrect Answers:
A. When set to “on”, DTP is spoken to the neighboring switch. On automatically enables ISL trunking on its port, regardless of the state of its neighboring switch. It remains an ISL trunk unless it receives an ISL packet that explicitly disables the ISL trunk. The Cisco TAC recommends that desirable trunking mode be configured on the ports.
D. In desirable mode, DTP is spoken to the neighboring switch. Desirable communicates to the neighboring switch that it is capable of being an ISL trunk, and would like the neighboring switch to also be an ISL trunk.
Reference:
http://www.cisco.com/warp/public/793/lan_switching/2.html

QUESTION NO: 9
The Testking corporate LAN consists of numerous Catalyst switches and a large number of VLANs. You are seeing an excessive amount of broadcasts across your trunk links. In an effort to reduce unnecessary traffic, VLAN Trunk Protocol (VTP) pruning is enabled. Which of the following statements is true regarding this change?
A. Traffic on VLAN 1 can be pruned.
B. Pruning eligibility is determined by the amount of ports assigned to a VLAN.
C. VTP pruning is a way to detect the removal of a VLAN within a VTP domain.
D. VTP version 2 is backward compatible with VTP version 1.
E. VTP pruning only affects traffic from VLANs that are pruning eligible.
Answer: E
Explanation:
VTP pruning enhances network bandwidth use by reducing unnecessary flooded traffic, such as broadcast, multicast, unknown, and flooded unicast packets. VTP pruning increases available bandwidth by restricting flooded traffic to those trunk links that the traffic must use to access the appropriate network devices. By default, VTP pruning is disabled. VTP pruning does not prune traffic from VLANs that are pruning-ineligible.
Incorrect Answers:
A. VLAN 1 is always pruning-ineligible, meaning traffic from VLAN 1 cannot be pruned.
B. Pruning eligibility is based only on the VLANs that need the given broadcast information across the trunks. It has nothing to do with the number of ports assigned to that VLAN.
C. VTP Pruning simply reduces the broadcast and multicast traffic. It does not change, add, or delete the VLANs in a VTP domain.
D. VTP version1 and VTP version2 are not interoperable on network devices in the same VTP domain. Every network device in the VTP domain must use the same VTP version. Do not enable VTP version2 unless every network device in the VTP domain supports version2.
Reference:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_4_2/config/vlans.htm#xtocid79802

QUESTION NO: 10
After performing some testing on a Catalyst switch in a lab, it is connected to the production network to another Catalyst switch via the supervisor Gigabit Ethernet port. Soon after this, users complain that they have lost all connectivity to the network.
What could have caused this to happen?
A. You did not issue the set spantree uplinkfast enable 1/1 command before connecting to the corporate switch.
B. You did not make the trunk mode set to on or desirable for the trunk to the supervisor of the other switch.
C. You did not make the VTP mode transparent in the new switch.
D. The dynamic CAM entries were not cleared after the new switch was connected to the network.
E. The new switch had the wrong VTP domain name.
Answer: C
Explanation:
The most likely cause of this happening is that the new switch was configured to participate in the VTP domain, but that it was set to server mode. The default mode is VTP server, which can override the VLAN information and get propagated to other switches in the network. In transparent mode, the switch will not participate in VTP, and it cannot override existing VTP settings.
Understanding the VTP Domain:
A VTP domain (also called a VLAN management domain) is made up of one or more interconnected network devices that share the same VTP domain name. A network device can be configured to be in one and only one VTP domain. You make global VLAN configuration changes for the domain using either the command-line interface (CLI) or Simple Network Management Protocol (SNMP).
By default, the Catalyst6500 series switch is in VTP server mode and is in the no-management domain state until the switch receives an advertisement for a domain over a trunk link or you configure a management domain. If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and the VTP configuration revision number. The switch ignores advertisements with a different management domain name or an earlier configuration revision number. If you configure the switch as VTP transparent, you can create and modify VLANs but the changes affect only the individual switch. When you make a change to the VLAN configuration on a VTP server, the change is propagated to all network devices in the VTP domain. VTP advertisements are transmitted out all trunk connections. VTP maps VLANs dynamically across multiple LAN types with unique names and internal index associations. Mapping eliminates excessive device administration required from network administrators.
Understanding VTP Modes:
You can configure a Catalyst6500 series switch to operate in any one of these VTP modes:
Server-In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP servers advertise their VLAN configuration to other network devices in the same VTP domain and synchronize their VLAN configuration with other network devices based on advertisements received over trunk links. VTP server is the default mode.
Client-VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.
Transparent-VTP transparent network devices do not participate in VTP. A VTP transparent network device does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, transparent network devices do forward VTP advertisements that they receive out their trunking LAN ports.
Incorrect Answers:
A. The set spantree uplinkfast enable command increases the path cost of all ports on the switch, making it unlikely that the switch will become the root switch. This obviously would not cause the problem described in this question.
B. This would affect the trunk coming up between the switches, but would not cause this kind of connectivity issue in this question. In this case, even if the trunk did not come up, end users would not even notice.
D. The CAM entries would have no impact, especially since no end stations were plugged into it in the lab.
E. The wrong VTP domain name would mean that this switch would not be participating in this particular VTP domain. In this specific case, this would have actually fixed the problem.

QUESTION NO: 11 You are trying to set up an Ethernet channel between switch A and switch B. After issuing the command “set port channel 3/1-2 on” on switch B, connectivity to switch B is lost. The following messages appear on switch B as a result of this.
Switch-B> (enable)
%SPANTREE-2-CHNMISCFG: STP loop – channel 3/1-2 is disabled in vlan 1.
%PAGP-5-PORTFROMSTP:Port 3/1 left bridge port 3/1-2
%PAGP-5-PORTFROMSTP:Port 3/2 left bridge port 3/1-2

You then disable the Ethernet Channel on Switch-B, but you still have no connectivity to Switch-A.
Which command will restore connectivity to switch A?
A. clear port error 3/1-2
B. set port enable 3/1-2
C. set trunk channel 3/1-2 desirable isl
D. set port channel 3/1-2 enable
Answer: B
Explanation:
The message clearly indicates that the ports 2/1-4 have been disabled. This is a consequence of spantree as shown by the “channel 3/1-2 is disabled in vlan 1” message. This will make the ports affected go into an err-disable state. To fix this, the ports need to be manually re-enabled with the “set port enable” command.

QUESTION NO: 12
A switch is configured for an ISL trunk, with the trunk mode set to on. A new switch is added to the network, but the trunk will not come up.
What is the probable cause of this problem?
A. The native VLANs are not the same.
B. The trunks need to be set to “on” or “auto”.
C. The trunks need to be set to “desirable” or “nonegotiate”.
D. The VTP domain names carried in the Dynamic Inter-Switch Link (DISL) messages are not the same.
E. The Unidirectional Link Detection timers are shorter than the Spanning Tree Protocol (STP) timers.
Answer: D
VTP domain names on an ISL trunk must be the same. DTP packets will not pass between switches that are in different VTP domains.
Incorrect Answers:
A. The VLANs can be different for each switch and the trunk will still come up if set up
correctly.
B, C. Since one end of the trunk is set to on, the other end can be set to either on, auto,
desirable, or nonegotiate for the trunk to come up.

E. These timers will have no bearing on the trunk formation.
Reference:
http://www.cisco.com/warp/public/793/lan_switching/2.html

QUESTION NO: 13 You are designing a new switched LAN and VLAN information will need to be shared between switches. What VLAN trunking protocol contains the following features?
-26 byte header and a 4 byte frame check sum -Supports up 1024 VLANs -Supports a single instance of spanning tree per-VLAN
A. ISL
B. 802.1d
C. 802.1q
D. 802.1v
E. 802.10
Answer: A
Explanation:
ISL is a Cisco proprietary protocol for interconnecting multiple switches and maintaining VLAN information as traffic goes between switches. ISL uses Per VLAN Spanning Tree (PVST) which runs one instance of Spanning Tree Protocol (STP) per VLAN. PVST allows for optimizing the root switch placement for each VLAN and supports load balancing of VLANs over multiple trunk links. With ISL, an Ethernet frame is encapsulated with a header that transports VLAN IDs between switches and routers. A 26-byte header that contains a 10-bit VLAN ID is prepended to the Ethernet frame. This 10 byte-VLAN ID provide for up to 1024 VLANs. The FCS field consists of four bytes in an ISL packet. This sequence contains a 32-bit CRC value, which is created by the sending MAC and is recalculated by the receiving MAC to check for damaged frames. The FCS is generated over the DA, SA, Length/Type, and Data fields. When an ISL header is attached, a new FCS is calculated over the entire ISL packet and added to the end of the frame

QUESTION NO: 14
A switch can belong to how many VTP domains?

A. 1
B. 2
C. 1 to 1005
D. 1 to 4096
E. It depends upon memory
F. It depends on the number of available IDB blocks
Answer: A Explanation
A Catalyst switch can only be configured to belong in only one VTP domain, using the “set VTP domain” command. If you attempt to use additional “set vtp domain” commands, you will simply overwrite the previous command and the switch will belong to the newly configured domain.

QUESTION NO: 15 The TestKing network administrator has set all TestKing switches to transparent VTP mode. What is a key advantage to configuring all switches in an enterprise network to VTP transparent mode?
A. It ensures consistency between VLAN numbering for all switches in the switched network.
B. It prevents network administrator’s form accidentally deleting VLAN information from all switches.
C. It allows for more rapid deployment of VLANs throughout the enterprise.
D. It reduces the size of the spanning tree network and improves STP convergence time as a result.
E. It reduces the total number of VLANs required in the enterprise network.
Answer: B
Explanation:
A major advantage to configuring all switches within a domain to transparent mode is that VLAN configuration settings on other switches will not get overridden. A mistake that many administrators make is installing a new switch into t domain when it is configured as a VTP server. The default mode is VTP server, which can override the VLAN information and get propagated to other switches in the network. This can mean the deletion of all of the other VLANs within the switched network. In transparent mode, the switch will not participate in VTP, and it cannot override existing VTP settings.
Understanding the VTP Domain:
A VTP domain (also called a VLAN management domain) is made up of one or more interconnected network devices that share the same VTP domain name. A network device can be configured to be in one and only one VTP domain. You make global VLAN configuration changes for the domain using either the command-line interface (CLI) or Simple Network Management Protocol (SNMP). By default, the Catalyst6500 series switch is in VTP server mode and is in the no-management domain state until the switch receives an advertisement for a domain over a trunk link or you configure a management domain. If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and the VTP configuration revision number. The switch ignores advertisements with a different management domain name or an earlier configuration revision number. If you configure the switch as VTP transparent, you can create and modify VLANs but the changes affect only the individual switch. When you make a change to the VLAN configuration on a VTP server, the change is propagated to all network devices in the VTP domain. VTP advertisements are transmitted out all trunk connections. VTP maps VLANs dynamically across multiple LAN types with unique names and internal index associations. Mapping eliminates excessive device administration required from network administrators.
Understanding VTP Modes:
You can configure a Catalyst6500 series switch to operate in any one of these VTP modes:
Server-In VTP server mode, you can create, modify, and delete VLANs and specify other configuration parameters (such as VTP version and VTP pruning) for the entire VTP domain. VTP servers advertise their VLAN configuration to other network devices in the same VTP domain and synchronize their VLAN configuration with other network devices based on advertisements received over trunk links. VTP server is the default mode.
Client-VTP clients behave the same way as VTP servers, but you cannot create, change, or delete VLANs on a VTP client.
Transparent-VTP transparent network devices do not participate in VTP. A VTP transparent network device does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, transparent network devices do forward VTP advertisements that they receive out their trunking LAN ports.

QUESTION NO: 16 A new Testking switch has been configured as a VTP client, and added to the existing VTP domain. Shortly after the ISL link is brought up to the rest of the network, the whole network goes down. What could have caused this to happen? (Choose the most likely option).
A. The configuration revision of the switch inserted was higher than the configuration revision of the VTP domain.
B. This is not an issue that could be related to the inserted switch since it was configured as a VTP client.
C. The inserted switch was incorrectly configured for VTP v2 and caused an unstable condition.
D. VLAN 1 was incorrectly deleted on the switch before insertion causing an unstable condition.
Answer: A
Explanation:
Even though the Catalyst switch is configured as a VTP client, and not a server, it can erase the information of an existing network. Cisco explains the problem as follows: How a Recently Inserted Switch Can Cause Network Problems This problem occurs when you have a large switched domain, which is all in the same VTP domain, and you want to add one switch in the network. This switch was previously used in the lab, and a good VTP domain name was entered. It was configured as a VTP client, and connected to the rest of the network. Then, the ISL link was brought up to the rest of the network. In just a few seconds, the whole network is down. What could have happened? The configuration revision of the switch you inserted was higher than the configuration revision of the VTP domain. Therefore, your recently-introduced switch, with almost no configured VLANs, has erased all VLANs through the VTP domain. This happens whether the switch is a VTP client or a VTP server. A VTP client can erase VLAN information on a VTP server. You can tell that this has happened when many of the ports in your network go into inactive state, but continue to be assigned to a nonexistent VLAN. Solution: Quickly reconfigure all of the VLANs on one of the VTP servers. What to Remember: Always make sure that the configuration revision of all switches inserted into the VTP domain is lower than the configuration revision of the switches already in the VTP domain. Reference: http://www.cisco.com/warp/customer/473/21.html#vtp_ts_cav

QUESTION NO: 17 The Testking network is bonding some of the Ethernet connections via PaGP in order to increase the backbone bandwidth. In PagP, what mode combination will allow a channel to be formed?
A. Auto-auto
B. Desirable-on
C. On-auto
D. Auto-desirable
Answer: D
Explanation:
The Port Aggregation Protocol (PAgP) modes are off, auto, desirable, and on. Only the
combinations auto-desirable, desirable-desirable, and on-on will allow a channel to be
formed.
The PAgP modes are explained below.

1.
off: PAgP will not run. The channel is forced to remain down.
2.
3.
desirable: PAgP is running actively. The formation of a channel is desired and initiated.

4.
On: PAgP will not run. The channel is forced to come up.
Only the combinations of auto-desirable, desirable-desirable, and on-on will allow a
channel to be formed. If a device on one side of the channel does not support PAgP, such
as a router, the device on the other side must have PAgP set to on.

QUESTION NO: 18 TestKing is using extended VLANs (VLAN IDs 1006-4094) on their switches. What should he VTP mode be set to before configuring extended-range VLANs?
A. Client
B. Server
C. Transparent
D. Client or Server
E. Client or Transparent
F. Server or Transparent
Answer: C
Explanation:
VTP transparent switches do not participate in VTP. A VTP transparent switch does not advertise its VLAN configuration and does not synchronize its VLAN configuration based on received advertisements. However, in VTP version 2, transparent switches do forward VTP advertisements that they receive from other switches from their trunk interfaces. You can create, modify, and delete VLANs on a switch in VTP transparent mode. The switch must be in VTP transparent mode when you create extended-range VLANs.

QUESTION NO: 19 Both ISL and 802.1Q is being used in the TestKing network. When comparing the differences in ISL and 802.1Q, which of the following are true? (Select three)
A. 802.1q allows the encapsulation of multiple trunks within a single trunk.
B. 802.1q supports fewer VLANs than ISL.
C. ISL is more efficient than 802.1q due to its smaller header size.
D. ISL supports the processing of untagged frames.
E. 802.1q uses a tag protocol ID of 0x8100
Answer: A, D, E
Both 802.1Q and ISL allows for the use of multiple trunks within any single trunk.
ISL supports the use of untagged frames on the trunk. All untagged frames are associated
with the native VLAN, which is VLAN 1 by default.
The IEEE 802.1Q specification defines the Ethertype field to be 8100 in the presence of a
VLAN ID. The entire packet format is shown below:

Incorrect Answers:
B. 802.1Q supports up to 4096 VLANS, while ISL supports a maximum of 1024.
C. ISL encapsulation adds 30 bytes to the entire frame, while the 802.1Q tag is only 4 bytes in length.

QUESTION NO: 20
The TestKing network is illustrated below:

In the shown diagram, Server TestKing1’s default gateway points to Router TestKing1’s VLAN1 interface and Server TestKing2’s default gateway points to Router TestKing2’s VLAN2 interface. Between Switch TestKing1 and TestKing2, both VLANs 1 and 2 are being forwarded over a trunk. When there is data transfer between the servers workstations, WS TestKing1 and WS TestKing2 see a lot of input traffic. How can we limit this problem?
A. Increase aging time on routers
B. Disable MAC address aging time on the switches
C. Disable ARP timeout on routers
D. Reduce MAC address aging time on the switches
E. Bring ARP aging time on Routers and MAC address aging time on switches close to each other
Answer: E
Explanation:
The problem described in this question is related to asymmetric routing, due to each workstation having different default gateways. The default ARP cache aging time on a router is 4 hours. The default aging time of the switch content-addressable memory (CAM) entry is 5 minutes. The ARP aging time of the host workstations is not significant for this discussion. However, the example sets the ARP aging time to 4 hours. This diagram illustrates this issue. This topology example includes Catalyst 6500s with Multilayer Switch Feature Cards (MSFCs) in each switch. The switches are interconnected via a trunk which carries traffic for VLAN 1 and VLAN 2.
Consequences of Asymmetric Routing:
Consider the case of the continuous ping of host B by host A. Remember that host A sends the echo packet to MSFC1, and host B sends the echo reply to MSFC2, which is in an asymmetric routing state. The only time that Switch 1 learns the source MAC of host B is when host B replies to an ARP request from MSFC1. This is because host B uses MSFC2 as its default gateway and does not send packets to MSFC1 and, consequently, Switch 1. Since the ARP timeout is 4 hours by default, Switch 1 ages the MAC address of host B after 5 minutes by default. Switch 2 ages host A after 5 minutes. As a result, Switch 1 must treat any packet with a destination MAC of host B as an unknown unicast. The switch floods the packet that comes from host A and is destined for host B out all ports. In addition, because there is no MAC address entry host B in Switch 1, there is no MLS entry as well. The echo reply packets that come from host B experience the same issue after the MAC address entry for host A ages on Switch 2. Host B forwards the echo reply to MSFC2, which in turn routes the packet and sends it out on VLAN 1. The switch does not have an entry host A in the MAC address table and must flood the packet out all ports in VLAN 1. Asymmetric routing issues do not break connectivity. However, asymmetric routing can cause excessive unicast flooding and MLS entries that are missing. There are three configuration changes that can remedy this situation:
1.
Adjust the MAC aging time on the respective switches to 14,400 seconds (4 hours) or longer.
2.
Change the ARP timeout on the routers to 5 minutes (300 seconds).
3.
Change the MAC aging time and ARP timeout to the same timeout value. Reference:
http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094afd.shtml

QUESTION NO: 21
The TestKing switched LAN is shown below:

Due to hardware failure on the link between switches TestKingA and TestKingB, Spanning Tree BPDUs from switch TestKingA are no longer received by switch TestKingB, but the link remains up (see the drawing) Provided LoopGuard feature is configured on all ports, which port will be put into ‘Loop-inconsistent’ state?
A. Port on switch TestKingC connecting to switch TestKingB
B. Port on switch TestKingB connecting to switch TestKingC
C. LoopGuard would not detect any issue in this scenario
D. Port on switch TestKingA connecting to switch TestKingB and port on switch TestKingB connecting to switch TestKingA
Answer: C
Understanding How Loop Guard Works:

Loop guard helps prevent bridging loops that could occur because of a uni-directional link failure on a point-to-point link. When enabled globally, the loop guard applies to all point-to-point ports on the system. Loop guard detects root ports and blocked ports and ensures that they keep receiving BPDUs from their designated port on the segment. If a loop guard enabled root or blocked port stop a receiving BPDUs from its designated port, it transitions to the loop-inconsistent blocking state, assuming there is a physical link error on this port. The port recovers from this loop-inconsistent state as soon as it receives a BPDU. You can enable loop guard on a per-port basis. When you enable loop guard, it is automatically applied to all of the active instances or VLANs to which that port belongs. When you disable loop guard, it is disabled for the specified ports. Disabling loop guard moves all loop-inconsistent ports to the listening state. Example:
The figure above illustrates the following configuration:
Switches A and B are distribution switches.
Switch C is an access switch.

Loop guard is enabled on ports 3/1 and 3/2 on Switches A, B, and C.
Enabling loop guard on a root switch has no effect but provides protection when a root
switch becomes a nonroot switch.
These caveats apply to loop guard:

Spanning tree always chooses the first operational port in the channel to send the BPDUs.
If that link becomes unidirectional, loop guard blocks the channel, even if other links in
the channel are functioning properly.

If a set of ports that are already blocked by loop guard are grouped together to form a
channel, spanning tree loses all the state information for those ports and the new channel
port may obtain the forwarding state with a designated role.

Note
You can enable UniDirectional Link Detection (UDLD) to help isolate the link failure. A loop may occur until UDLD detects the failure, but loop guard will not be able to detect it.
Loop guard has no effect on a disabled spanning tree instance or a VLAN.
Reference:
http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_guide_chapter09186a0080160a
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