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Switching Technology > Revision questions > Flashcards

Revision questions Flashcards

1
Q

What is the boot sequence for a switch?

A

Step 1: First, the switch loads a power-on self-test (POST) program stored in ROM.
POST checks the CPU subsystem. It tests the CPU, DRAM, and the portion of the flash
device that makes up the flash file system.

Step 2: Next, the switch loads the boot loader software. The boot loader is a small
program stored in ROM that is run immediately after POST successfully completes.

Step 3: The boot loader performs low-level CPU initialization. It initializes the CPU
registers, which control where physical memory is mapped, the quantity of memory, and
its speed.

**Step 4: The boot loader initializes the flash file system on the system board.

Step 5: Finally, the boot loader locates and loads a default IOS operating system
software image into memory and gives control of the switch over to the IOS.

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2
Q

What is the startup-config file called and where is it located?

A

The startup-config file is called config.text and is located in flash

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3
Q

Which feature on a switch is useful when the speed and duplex settings of the device connecting to the port are unknown or may change?

A

Autonegotiation

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4
Q

What are runt frames?

A

Ethernet frames that are shorter than the 64-byte minimum allowed
length are called runts.

Malfunctioning NICs are the usual cause of excessive runt
frames, but they can also be caused by collisions

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5
Q

What are Giants?

A

Ethernet frames that are larger than the maximum allowed size are called giants

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6
Q

Which statement is true about broadcast and collision domains?

A

Adding a switch to a network will increase the size of the broadcast domain.

Explain: A switch that receives a broadcast frame will forward the frame out all other interfaces, including interfaces that connect to other switches. These switches will also perform the same forwarding action. By adding more switches to the network, the size of the broadcast domain increases.

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7
Q

What is one function of a Layer 2 switch?

  • Forwards data based on logical addressing
  • Duplicates the electrical signal of each frame to every port
  • Learns the port assigned to a host by examining the destination MAC address
  • Determines which interface is used to forward a frame based on the destination MAC address
A

Determines which interface is used to forward a frame based on the destination MAC address

Explain:
A switch builds a MAC address table of MAC addresses and associated port numbers by examining the source MAC address found in inbound frames. To forward a frame onward, the switch examines the destination MAC address, looks in the MAC address for a port number associated with that destination MAC address, and sends it to the specific port. If the destination MAC address is not in the table, the switch forwards the frame out all ports except the inbound port that originated the frame.

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8
Q

What is the significant difference between a hub and a Layer 2 LAN switch?

A

A switch creates many smaller collision domains, and a hub increases the size of a single collision domain.

Explain: Hubs operate only at the physical layer, forwarding bits as wire signals out all ports, and extend the collision domain of a network. Switches forward frames at the data link layer and each switch port is a separate collision domain, and thus more, but smaller, collision domains are created. Switches do not manage broadcast domains because broadcast frames are always forwarded out all active ports.

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9
Q

What will a Cisco LAN switch do if it receives an incoming frame and the destination MAC address is not listed in the MAC address table?

A

Forward the frame out all ports except the port where the frame is received.

Explain:
A LAN switch populates the MAC address table based on source MAC addresses. When a switch receives an incoming frame with a destination MAC address that is not listed in the MAC address table, the switch forwards the frame out all ports except for the ingress port of the frame. When the destination device responds, the switch adds the source MAC address and the port on which it was received to the MAC address table.

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10
Q

Which switch characteristic helps alleviate network congestion when a 10 Gbps port is forwarding data to a 1 Gbps port?

A

Frame buffering

Explain:
The large frame buffers on a switch hold the ingress traffic until such time that the slower egress port can transmit the data. This reduces the number of dropped frames and alleviates network congestion.

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11
Q

Which switching method makes use of the FCS value?

A

Store-and-forward

Explain:
The store-and-forward method performs error checking on the frame using the frame-check sequence (FCS) value before sending the frame. The FCS value is the last field in the frame.

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12
Q

What does the term “port density” represent for an Ethernet switch?

A

The number of available ports

Explain:
The term port density represents the number of ports available in a switch. A one rack unit access switch can have up to 48 ports. Larger switches may support hundreds of ports.

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13
Q

Which information does a switch use to keep the MAC address table information current?

A

The source MAC address and the incoming port

Explain:
To maintain the MAC address table, the switch uses the source MAC address of the incoming packets and the port that the packets enter. The destination address is used to select the outgoing port.

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14
Q

Which two statements are true about half-duplex and full-duplex communications? (Choose two.)

  • Full duplex offers 100 percent potential use of the bandwidth.
  • Half duplex has only one channel.
  • All modern NICs support both half-duplex and full-duplex communication.
  • Full duplex allows both ends to transmit and receive simultaneously.
  • Full duplex increases the effective bandwidth.
A
  • Full duplex allows both ends to transmit and receive simultaneously.
  • Full duplex increases the effective bandwidth.

Explain:
Full-duplex communication allows both ends to transmit and receive simultaneously, offering 100 percent efficiency in both directions for a 200 percent potential use of stated bandwidth. Half-duplex communication is unidirectional, or one direction at a time. Gigabit Ethernet and 10 Gb/s NICs require full duplex to operate, and do not support half-duplex operation.

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15
Q

Which type of address does a switch use to build the MAC address table?

  • Destination IP address
  • Source IP address
  • Destination MAC address
  • Source MAC address
A
  • Source MAC address

Explain:
When a switch receives a frame with a source MAC address that is not in the MAC address table, the switch will add that MAC address to the table and map that address to a specific port. Switches do not use IP addressing in the MAC address table.

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16
Q

Which option correctly describes a switching method?

  • Cut-through: makes a forwarding decision after receiving the entire frame
  • Store-and-forward: forwards the frame immediately after examining its destination MAC address
  • Cut-through: provides the flexibility to support any mix of Ethernet speeds
  • Store-and-forward: ensures that the frame is free of physical and data-link errors
A
  • Store-and-forward: ensures that the frame is free of physical and data-link errors

Explain:
Store-and-forward switching performs an error check on an incoming frame after receiving the entire frame on the ingress port. Switches which use this method have the flexibility to support any mix of Ethernet speeds. The cut-through method begins the forwarding process after the destination MAC address of an incoming frame is looked up and the egress port has been determined.

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17
Q

Which network device can serve as a boundary to divide a Layer 2 broadcast domain?

  • Router
  • Ethernet bridge
  • Ethernet hub
  • Access point
A
  • Router

Explain:
Layer 1 and 2 devices (LAN switch and Ethernet hub) and access point devices do not filter MAC broadcast frames. Only a Layer 3 device, such as a router, can divide a Layer 2 broadcast domain.

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18
Q

What is the purpose of frame buffers on a switch?

  • They provide a basic security scan on received frames.
  • They provide temporary storage of the frame checksum.
  • They execute checksum values before transmission.
  • They hold traffic, thus alleviating network congestion.
A
  • They hold traffic, thus alleviating network congestion.

Explain
Switches have large frame buffers that allow data waiting to be transmitted to be stored so the data will not be dropped. This feature is beneficial especially if the incoming traffic is from a faster port than the egress port used for transmitting.

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19
Q

Which network device can be used to eliminate collisions on an Ethernet network?

  • Firewall
  • Hub
  • Router
  • Switch
A
  • Switch

A switch provides micro-segmentation so that no other device competes for the same Ethernet network bandwidth.

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20
Q

What happens to a port that is associated with VLAN 10 when the administrator deletes VLAN 10 from the switch?

  • The port becomes inactive.
  • The port goes back to the default VLAN.
  • The port automatically associates itself with the native VLAN.
  • The port creates the VLAN again.
A
  • The port becomes inactive.

If the VLAN that is associated with a port is deleted, the port becomes inactive and cannot communicate with the network any more. To verify that a port is in an inactive state, use the show interfaces switchport command.

21
Q

In which memory location are the VLAN configurations of normal range VLANs stored on a Catalyst switch?

  • Flash
  • NVRAM
  • RAM
  • ROM
A
  • Flash

When a normal range VLAN is created the configuration information of the VLAN is stored in flash in the vlan.dat file.

22
Q

An administrator is investigating a failure on a trunk link between a Cisco switch and a switch from another vendor. After a few show commands, the administrator notices that the switches are not negotiating a trunk. What is a probable cause for this issue?

  • Both switches are in trunk mode.
  • Both switches are in non-negotiate mode.
  • Switches from other vendors do not support DTP.
  • DTP frames are flooding the entire network.
A
  • Switches from other vendors do not support DTP.

Explain:
DTP is a Cisco proprietary protocol. Non-Cisco switches do not support DTP.

23
Q

What is the purpose of the vlan.dat file on a switch?

  • It holds the running configuration.
  • It holds the saved configuration.
  • It holds the VLAN database.
  • It holds the operating system.
A
  • It holds the VLAN database.

Explain:
The VLAN database (vlan.dat) contains information about normal range VLANs such as the VLAN number, name, and VTP mode.

24
Q

What is the purpose of setting the native VLAN separate from data VLANs?

  • The native VLAN is for carrying VLAN management traffic only.
  • The security of management frames that are carried in the native VLAN can be enhanced.
  • A separate VLAN should be used to carry uncommon untagged frames to avoid bandwidth contention on data VLANs.
  • The native VLAN is for routers and switches to exchange their management information, so it should be different from data VLANs.
A
  • A separate VLAN should be used to carry uncommon untagged frames to avoid bandwidth contention on data VLANs.

Explain:
When a Cisco switch trunk port receives untagged frames (unusual in well-designed networks), it forwards these frames to the native VLAN. When the native VLAN is moved away from data VLANs, those untagged frames will not compete for bandwidth in the data VLANs.

The native VLAN is not designed for carrying management traffic, but rather it is for backward compatibility with legacy LAN scenarios.

25
Q

When a Cisco switch receives untagged frames on a 802.1Q trunk port, which VLAN ID is the traffic switched to by default?

  • Unused VLAN ID
  • Native VLAN ID
  • Data VLAN ID
  • Management VLAN ID
A
  • Native VLAN ID

Explain:
A native VLAN is used to forward untagged frames that are received on a Cisco switch 802.1Q trunk port. Untagged frames that are received on a trunk port are not forwarded to any other VLAN except the native VLAN.

26
Q

A network administrator is determining the best placement of VLAN trunk links. Which two types of point-to-point connections utilize VLAN trunking?​ (Choose two.)

  • Between two switches that utilize multiple VLANs
  • Between a switch and a client PC
  • Between a switch and a server that has an 802.1Q NIC
  • Between a switch and a network printer
  • Between two switches that share a common VLAN
A
  • Between two switches that utilize multiple VLANs
  • Between a switch and a server that has an 802.1Q NIC

Explain:
VLAN trunk links are used to allow all VLAN traffic to propagate between devices such as the link between a switch and a server that has an 802.1Q-capable NIC. Switches can also utilize trunk links to routers, servers, and to other switches.

27
Q

What are three primary benefits of using VLANs? (Choose three.)

  • Security
  • A reduction in the number of trunks
  • Cost reduction
  • End user satisfaction
  • Improved IT Staff efficiency
A
  • Security
  • Cost reduction
  • Improved IT Staff efficiency

Explain:
Security, cost reduction, and improved IT staff efficiency are all benefits of using VLANs, along with higher performance, broadcast storm mitigation, and simpler project and application management.

End users are not usually aware of VLANs, and VLANs do require configuration. Because VLANs are assigned to access ports, they do not reduce the number of trunk links.

28
Q

On a Cisco switch, where is extended range VLAN information stored?

  • Running configuration file
  • Startup configuration file
  • NVRAM
  • Flash
A
  • Running configuration file

Explain:
Extended range VLANs, 1006 through 4094, are not written to the vlan.dat file but are saved in the running configuration file.

29
Q

In which location are the normal range VLANs stored on a Cisco switch by default?

  • Flash memory
  • Startup-config
  • Running-config
  • RAM
A
  • Flash memory

Explain:
Normal range VLANs are stored in a file called vlan.dat and located in the flash memory.

30
Q

Which distinct type of VLAN is used by an administrator to access and configure a switch?

  • Default VLAN
  • Native VLAN
  • Data VLAN
  • Management VLAN
A
  • Management VLAN

Explain:
A management VLAN is used to remotely access and configure a switch. Data VLANs are used to separate a network into groups of users or devices. The default VLAN is the initial VLAN all switch ports are placed in when loading the default configuration on a switch. The 802.1Q trunk port places untagged traffic on the native VLAN.

31
Q

For what reason would a network administrator use the show interfaces trunk command on a switch?

  • To view the native VLAN
  • To examine DTP negotiation as it occurs
  • To verify port association with a particular VLAN
  • To display an IP address for any existing VLAN
A
  • To view the native VLAN

Explain:
The show interfaces trunk command displays the ports that are trunk ports, the trunking mode, the encapsulation type, the trunk status, the native VLAN, and the allowed VLANs on the link.

32
Q

Where is the vlan.dat file stored on a switch?

  • In RAM
  • In NVRAM
  • In flash memory
  • On the externally attached storage media or internal hard drive
A
  • In flash memory

Normal range VLAN configurations are stored within a VLAN database file, called vlan.dat, which is located in the flash memory of the switch.

33
Q

If an organization is changing to include Cisco IP phones in its network, what design feature must be considered to ensure voice quality?

  • Voice traffic needs to be tagged with the native VLAN.
  • A separate VLAN is needed for voice traffic.
  • Additional switch ports that are dedicated to Cisco IP phones are required.
  • Voice traffic and data traffic require separate trunk links between switches.
A
  • A separate VLAN is needed for voice traffic.

Explain:
A PC commonly connects to an IP phone and the IP phone, in turn, connects to a switch. The phone does not require a separate port. Because voice traffic cannot tolerate much packet delay, it needs to be in a separate VLAN. The voice VLAN can be configured to provide quality of service (QoS), which will ensure that the voice traffic has a higher priority than data traffic.

34
Q

A Cisco switch currently allows traffic tagged with VLANs 10 and 20 across trunk port Fa0/5. What is the effect of issuing a switchport trunk allowed vlan 30 command on Fa0/5?

  • It allows VLANs 1 to 30 on Fa0/5.
  • It allows VLANs 10, 20, and 30 on Fa0/5.
  • It allows only VLAN 30 on Fa0/5.
  • It allows a native VLAN of 30 to be implemented on Fa0/5.
A
  • It allows only VLAN 30 on Fa0/5.

The switchport trunk allowed vlan 30 command allows traffic that is tagged with VLAN 30 across the trunk port. Any VLAN that is not specified in this command will not be allowed on this trunk port.

35
Q

A PC is to access a web server on another network. Which inter-VLAN method will provide the highest bandwidth at Layer 3 and also provide a default gateway for the PC?

  • Router on a stick
  • Multilayer switch with routing enabled
  • Trunked interface between the router and the switch
  • Multiple physical interfaces on the router, all connected to a Layer 2 switch
A
  • Multilayer switch with routing enabled
  • A router-on-a-stick design is the same as having a trunked interface between the router and the switch. This design works, but does not scale well because all VLANs must traverse the one connection between the router and the switch. Multiple physical interfaces on the router would be faster than the router-on-a-stick design, but a router has a limited number of physical interfaces. Layer 3 switches with routing enabled have more Ethernet ports as well as the ability to route.
36
Q

Which scalable method must be implemented in order to provide inter-VLAN routing on a switched network with more than 1000 VLANs?

  • Configuring static routes on a Layer 2 switch device
  • Routing traffic internally to a Layer 3 switch device
  • Connecting each physical router interface to a different physical switch port, with each switch port assigned to a different VLAN
  • Connecting a router interface to a switch port that is configured in trunk mode to route packets between VLANs, with each VLAN assigned to a router subinterface​
A
  • Routing traffic internally to a Layer 3 switch device

Explain:

Layer 2 switches are able to perform static routing, but this method is inefficient with a large number of VLANs. Multilayer switching is more scalable than any other inter-VLAN routing implementation, with traffic being routed internally to the switch device.

In router-on-a-stick inter-VLAN routing, where a single physical interface routes traffic among multiple VLANs on a network, there is no practical scalability.

The legacy inter-VLAN routing is very inefficient and is no longer used in switched networks, because each VLAN requires a physical router interface that is connected to a different physical switch port.

37
Q

When configuring a router as part of a router-on-a-stick inter-VLAN routing topology, where should the IP address be assigned?

  • To the interface
  • To the sub-interface
  • To the SVI
  • To the VLAN
A
  • To the sub-interface

Explain:
The IP address and the encapsulation type should be assigned to each router sub-interface in a router-on-a-stick inter-VLAN topology.

38
Q

A small college uses VLAN 10 for the classroom network and VLAN 20 for the office network. What is needed to enable communication between these two VLANs while using legacy inter-VLAN routing?

  • A router with at least two LAN interfaces should be used.
  • Two groups of switches are needed, each with ports that are configured for one VLAN.
  • A router with one VLAN interface is needed to connect to the SVI on a switch.
  • A switch with a port that is configured as trunk is needed to connect to a router.
A
  • A router with at least two LAN interfaces should be used.

Explain:
With legacy inter-VLAN routing, different physical router interfaces are connected to different physical switch ports. The switch ports that connect to the router are in access mode, each belonging to a different VLAN.

Switches can have ports that are assigned to different VLANs, but communication between VLANs requires routing function from the router.

39
Q

What is a disadvantage of using multilayer switches for inter-VLAN routing?

  • Multilayer switches have higher latency for Layer 3 routing.
  • Multilayer switches are more expensive than router-on-a-stick implementations.
  • Spanning tree must be disabled in order to implement routing on a multilayer switch.
  • Multilayer switches are limited to using trunk links for Layer 3 routing.
A
  • Multilayer switches are more expensive than router-on-a-stick implementations.

Explain:
The main disadvantage of the multilayer switches is their higher cost. Because both routing and switching are done in hardware, multilayer switches are faster than router-on-a-stick.

40
Q

Which type of inter-VLAN communication design requires the configuration of multiple subinterfaces?

  • Router on a stick
  • Routing via a multilayer switch
  • Routing for the management VLAN
  • Legacy inter-VLAN routing
A
  • Router on a stick

Explain:
The router-on-a-stick design always includes sub-interfaces on a router. When a multilayer switch is used, multiple SVIs are created. When the number of VLANs equals the number of ports on a router, or when the management VLAN needs to be routed, any of the inter-VLAN design methods can be used.

41
Q

What is a disadvantage of using router-on-a-stick inter-VLAN routing?

  • Does not support VLAN-tagged packets
  • Requires the use of more physical interfaces than legacy inter-VLAN routing
  • Does not scale well beyond 50 VLANs
  • Requires the use of multiple router interfaces configured to operate as access links
A
  • Does not scale well beyond 50 VLANs

Explain;
Router-on-a-stick inter-VLAN routing does not scale beyond 50 VLANs. The router can receive VLAN-tagged packets and send VLAN-tagged packets to a destination.

Router-on-a-stick inter-VLAN routing can utilize a single router interface as a trunk link to receive and forward VLAN traffic and does not require multiple interfaces.

42
Q

What is the meaning of the number 10 in the encapsulation dot1Q 10 native router subinterface command?​

  • The interface number
  • The sub-interface number​
  • The subnet number
  • The VLAN ID
A
  • The VLAN ID
43
Q

While configuring inter-VLAN routing on a multilayer switch, a network administrator issues the no switchport command on an interface that is connected to another switch. What is the purpose of this command?

  • To create a routed port for a single network
  • To provide a static trunk link
  • To create a switched virtual interface
  • To provide an access link that tags VLAN traffic
A
  • To create a routed port for a single network

Explain:
When a Layer 2 interface on a multilayer switch is configured with the no switchport command, it becomes a routed port. A routed port is configured with an IP address for a specific subnet.

44
Q

A network administrator enters the following command sequence on a Cisco 3560 switch. What is the purpose of these commands?

Switch(config)# interface gigabitethernet 0/1
Switch(config-if)# no switchport

  • To shut down the Gi0/1 port
  • To make the Gi0/1 port a routed port
  • To enable the Gi0/1 port as a switch virtual interface
  • To enable the Gi0/1 port as a bridge virtual interface
A
  • To make the Gi0/1 port a routed port

Explain:
By default, the physical ports on a 3560 switch are Layer 2 interfaces. To make them routed ports, the interface command no switchport should be used. The other options do not describe the purpose of this command.

45
Q

What operational mode should be used on a switch port to connect it to a router for router-on-a-stick inter-VLAN routing?

  • Trunk
  • Access
  • Dynamic auto
  • Dynamic desirable
A
  • Trunk

Routers do not support Dynamic Trunking Protocol, and access mode is used to connect hosts.

46
Q

Which sentence correctly describes the SVI inter-VLAN routing method?

  • Sub-interfaces have to be created.
  • The encapsulation type must be configured on the SVI.
  • An SVI is needed for each VLAN.
  • A physical interface is needed for every VLAN that is created.
A
  • An SVI is needed for each VLAN.

Explain:
In order to create SVI inter-VLAN routing on a Layer 3 switch, the VLAN must exist in the database and the SVI must be explicitly created. The only exception is VLAN1, which is created by default.

47
Q

How is traffic routed between multiple VLANs on a multilayer switch?

  • Traffic is routed via physical interfaces.
  • Traffic is routed via internal VLAN interfaces.
  • Traffic is broadcast out all physical interfaces.
  • Traffic is routed via sub-interfaces.
A
  • Traffic is routed via internal VLAN interfaces.

Explain:
Multilayer switches can perform inter-VLAN routing by the use of internal VLAN interfaces. External physical interfaces can receive traffic but are not necessary for routing functions.

When routing between VLANs, any broadcast traffic that is received on a VLAN would remain on ports that are members of that VLAN. Sub-interfaces are not usable for inter-VLAN routing on multilayer switches.

48
Q

What is required to perform router-on-a-stick inter-VLAN routing?

  • A Layer 2 switch that is configured with multiple trunk ports
  • A router with multiple physical interfaces
  • A multilayer switch
  • A router that is configured with multiple sub-interfaces
A
  • A router that is configured with multiple sub-interfaces

With router-on-a-stick inter-VLAN routing, a single physical router interface is used to route packets between multiple VLANs if the interface is configured with multiple sub-interfaces.

A separate sub-interface is needed for each VLAN that will be routed. Because the router is performing all routing functions, a multilayer switch is not required.

49
Q

An administrator was troubleshooting a router-on-a-stick topology and concluded that the problem was related to the configuration of VLANs on the router subinterfaces. Which two commands can the administrator use in the router to identify the problem? (Choose two.)

  • show controllers
  • show ip interface
  • show ip protocols
  • show running-config
  • show vlan
A
  • show ip interface
  • show running-config

The show ip interface and show running-config commands can be useful in troubleshooting routing issues like wrong VLAN IDs that are assigned to sub-interfaces.

The show controllers and show ip protocols commands do not display any information about VLANs. The show vlan command is not useful to show information about the router sub-interfaces.

Switching Technology (4 decks)

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