Activitats d’Emprenedoria i Incubació
10. RECERCA I TRANSFERÈNCIA DE CONEIXEMENT
10.2 Grups de Recerca
1. Which of the following is a Layer 2 broadcast?
A. AAAA.AAAA.AAAA
2. Which statement best describes how a switch handles broadcasts by default?
A. All broadcasts are filtered.
B. All broadcasts are forwarded.
C. They are forwarded only to the VLANs for which they are intended.
D. They are forwarded to the VTP server, which
performs broadcast forwarding for the VTP domain.
Answer: B. The default behavior of a switch is to forward
broadcasts. VLANs can be configured to limit broadcast propagation, but this is not a default behavior.
3. A switch receives a frame with a destination MAC address of aaaa.aaaa.aaaa. The switch does not know what port should be used to reach the device with that MAC address. What will the switch do with this frame?
A. The switch will filter the frame.
B. The switch will forward the frame out all ports.
C. The switch will forward the frame out all ports except the port on which it was received.
D. The switch will perform a reverse ARP operation to get the MAC address, then the frame will be unicast.
Answer: C. If the switch does not know which port to forward a frame out of, the switch will forward the frame out all ports except that which it was received.
4. A switch receives a frame with a destination MAC address of bbbb.bbbb.bbbb on port 0/3. The switch knows the destination address can be reached out the same port. What will the switch do ?
A. The switch will filter the frame.
B. The switch will forward the frame to the destination.
C. The switch will forward the frame out all ports except the one it was received on.
D. The switch will send a message to the source, indicating that no more frames for this destination should be sent to the switch.
Answer: A. The switch will filter the frame; that is, the frame will not be forwarded out any ports.
5. What two sources of information do switches use to build their MAC address tables? (Choose two.)
A. The source address of incoming frames.
B. The destination address of incoming frames.
C. Statically configured MAC addresses.
D. VTP servers.
E. MHOST files.
Answer: A, C. The main source of MAC addresses that are entered into the MAC table is the source address of incoming frames. The destination address doesn’t help build the table; that address is either already known, or the frame is flooded. Neither action adds an entry to the MAC table. MAC addresses can also be statically entered. VTP servers have nothing to do with building the MAC table, and there’s no such thing as an MHOST file in Cisco.
6. By default, what frames are flooded out all ports except the port upon which it was received? Choose two.
A. Frames destined for a known unicast address.
B. Frames destined for an unknown unicast address.
C. Broadcast frames.
D. VTP frames.
E. STP frames.
Answer: B, C. Both broadcast frames and frames destined for an unknown unicast address are flooded out all ports except the port it was received on.
7. What command allows viewing of the MAC address table ? A. show Layer2 address
B. show mac-address-table C. show macs
D. show table Answer: B.
8. Which of the following are port security violation modes on a Cisco 2950 switch? (Choose three.)
A. Shutdown B. Report C. Reload Port D. Request E. Restrict F. Protect G. Purge MAC H. Preserve Answer: A, E, F.
9. Which of the following is true of port security on a Cisco 2950 switch? Choose two.
A. The default violation mode is Shutdown.
B. The default violation mode is Restrict.
C. The default violation mode is Protect.
D. Any switchport can be configured with port security.
E. Ports connecting to end hosts cannot be configured with port security.
F. Ports connecting to other switches cannot be configured with port security.
Answer: A, F. The default mode is shutdown, and ports connecting to other switches cannot use port security. To configure a port as not having a switch attached to that port, configure it as an access port (switch mode access).
10. In Cisco port security, what is true of the term “sticky secure MAC address”? (Choose two.)
A. Once configured, the address cannot be removed from the switch without erasing the router
configuration.
B. No other secure MAC addresses can be configured on a port once a sticky secure MAC has been
configured.
C. The sticky MAC address will be learned from the first MAC address the switch learns on that port.
D. The sticky MAC address will be added to the running configuration of the switch.
E. The sticky MAC address cannot connect to any other port on the switch except the one it is learned on.
Answer: C, D. By configuring switchport port-security mac-address sticky on an interface already configured for port-security, the MAC source of the next frame received on that port is the secure MAC address. Additionally, the sticky MAC will be added to the
running configuration of the switch. Saving the running configuration will result in that secure MAC address remaining on that port after a switch reboot.
11. What protocol runs at Layer 2 and prevents loops from forming in networks with redundant paths?
A. TCP B. IP C. STP D. UDP E. ISL
Answer: C. Spanning-Tree Protocol (STP) runs on switches to prevent loops from forming when more than one path between destinations exists.
12. Which statement best describes how STP handles broadcasts?
A. Broadcasts travel the single path between destinations, like all other data.
B. In order to ensure the entire network receives the broadcast, broadcasts are “leaked” through blocked ports.
C. STP implicitly denies broadcasts.
D. STP sends broadcasts out root ports only.
Answer: A. STP takes no particular action toward broadcasts;
broadcasts will travel the single path between destinations like all other data.
13. Your network has four switches. The priorities and MAC addresses are:
Priority MAC Address Switch 1 32768 1111.1111.1111 Switch 2 16384 2222.2222.2222 Switch 3 8194 3333.3333.3333 Switch 4 8194 4444.4444.4444
Which statements are true of the root bridge?
A. Switch 1 will become the root bridge.
B. Switch 2 will become the root bridge.
C. Switch 3 will become the root bridge.
D. Switch 4 will become the root bridge.
Answer: C. The lowest BID wins the election for root port, and the BID consists of the priority and the MAC address. For example, Switch 3’s BID is 8194:3333.3333.333, and Switch 4’s BID is
8194.4444.4444.4444. Since their priorities are the same, the difference is that Switch 3’s MAC address is lower than Switch 4’s, making Switch 3’s BID lower.
14. Your network has four switches. The priorities and MAC addresses are:
Priority MAC Address
Switch 1 4096 1111.1111.1111 Switch 2 16384 2222.2222.2222 Switch 3 16384 3333.3333.3333 Switch 4 32768 4444.4444.4444
Which statements are true of the root bridge ? A. Switch 1 will become the root bridge.
B. Switch 2 will become the root bridge.
C. Switch 3 will become the root bridge.
D. Switch 4 will become the root bridge.
E. The MAC address comes into play in this election.
F. The MAC address does not matter in this election.
Answer: A, F. The lowest BID becomes the root election. Switch 1 has the lowest priority of the four, guaranteeing it the lowest BID.
The MAC address is part of the BID, but no matter what the MACs are, Switch 1 will still have the lowest BID.
15. Your root switch is connected to another switch by three trunks.
You run show spanning vlan 10 on your root switch and receive the following output:
Which of the following statements is true? (Choose three.) A. Hello BPDUs are originating from this switch.
B. Hello BPDUs are being received from another switch.
C. This switch had the highest BID during the root bridge election.
D. This switch had the lowest BID during the root bridge election.
E. This switch has an EtherChannel configured on it.
F. This switch’s forwarding interface is port 0/1 (po1).
Answer: A, D, E. This is the root bridge, so Hello BPDUs are
originating from this switch and are forwarded by other switches. To become the root bridge, the switch had to have the lowest BID during the election. Finally, “po1” indicates Port-channel1, which is an
EtherChannel.
16. Your root switch is connected to another switch by three trunks.
You run show spanning vlan 10 on your root switch and receive the following output:
You notice that all three ports connecting to the other switch are in Forwarding mode. Which of the following is true?
A. There is an error with STP, because only one port can be in Forwarding mode.
B. There is an error with the VLAN configuration.
C. The other switch is rebooting, resulting in all three ports going into Forwarding mode. Once the other switch finishes coming back up, two of these ports will go into Blocking mode.
D. There is no problem; this is normal.
Answer: D. All ports on the root switch will be in Forwarding mode.
17. How many root ports can a non-root switch have for a given VLAN?
A. One.
B. Two – one primary root port and one backup root port.
C. As many as STP assigns the switch.
D. None – nonroot switches don’t have root ports.
Answer: A. Nonroot switches have one root port per VLAN – period.
18. By default, how often does a root bridge send out Hello BPDUs?
A. Every second.
B. Every two seconds.
C. Every minute.
D. Every two minutes.
E. Never – root bridges don’t send BPDUs.
Answer: B. Root bridges send Hello BPDUs every two seconds.
19. The Hello BPDU value ForwardDelay determines the length of which two STP port states ? (Choose two.)
A. Blocking B. Listening C. Learning D. Forwarding
Answer: B, C. ForwardDelay determines how long ports stay in the Listening and Learning stages.
20. Which of the following is true of the MaxAge timer carried in Hello BPDUs? (Choose two.)
A. This timer defines how long the root bridge waits to send the Hello BPDUs.
B. This timer defines how long any bridge should wait to attempt running the STP algorithm once Hello BPDUs stop being received.
C. This timer defines how long a port remains in the listening and learing stages.
D. The default setting for this timer is two seconds.
E. The default setting for this timer is 15 seconds.
F. The default setting for this timer is 20 seconds.
Answer: B, F. Choices A and D are true of the Hello Time timer; C and E are true of the ForwardDelay timer.
21. During which of the following states does a port forward data frames?
A. Listening, learning, and forwarding.
B. Learning and forwarding.
C. Listening and forwarding.
D. Forwarding only.
Answer: D. The only time a port can forward data frames is when it’s in Forwarding state.
22. Which of the following is true of EtherChannels? (Choose three.) A. EtherChannels are logical bundling of physical links.
B. EtherChannels are a physical bundling of physical links.
C. Links do not have to be trunked to part of an EtherChannel.
D. Links must be trunked to be part of an EtherChannel.
E. Up to ten physical links can belong to a single EtherChannel.
F. STP considers an EtherChannel to be a single link, but a failure of one of the links making up the EtherChannel forces STP to recalculate the spanning tree.
G. STP considers an EtherChannel to be a single link, and a failure of one of the links making up the EtherChannel will not result in STP recalculation.
Answers: A, D, G. An EtherChannel is a logical bundling of up to eight trunked, parallel Ethernet links. STP sees an EtherChannel as a single logical link, and a failure of one of the physical links will not result in STP recalculation.
23. Which of the following devices can route packets between VLANs?
Choose two.
Answers: A, C. Routers, multilayer switches, and Layer 3 switches can all route packets between VLANs. A simple Layer 2 switch cannot, nor can a hub, repeater, or concentrator.
24. HostA and HostB are in VLAN 10. HostC and HostD are in VLAN 20. Assuming the VLANs have been configured correctly but routing is not taking place, which of the following is true? Choose four.
A. HostA can ping HostB.
B. HostA cannot ping HostB.
C. HostA cannot ping HostC.
D. HostB can ping HostC.
E. HostB can ping HostD.
F. HostC can ping HostD.
G. HostC cannot ping HostD.
H. HostD cannot ping HostA.
Answer: A, C, F, H. Typically, hosts in the same VLAN are on the same subnet. Communication between VLANs requires routing take place. Hosts in the same VLAN will be able to ping each other, but hosts in different VLANs will not be able to do so.
25. Which of the following is true of trunking?
A. ISL is a Cisco-proprietary protocol, and can therefore be used to configure trunking between non-Cisco devices.
B. 802.1q is the industry standard, and can therefore be used to configure trunking between a non-Cisco device and a Cisco switch.
C. ISL encapsulates the entire frame.
D. 802.1q encapsulates the entire frame.
E. ISL understands the concept of the native vlan.
F. 802.1q understands the concept of the native vlan.
Answer: B, C, F. Answer “A” is half-true; ISL is a Cisco-proprietary protocol, which means it cannot be used for trunking between non-Cisco devices. ISL does encapsulate the entire frame, where 802.1q adds a header identifying the VLAN ID. ISL does not allow the use of native vlans.
26. Which is true of native vlans?
A. ISL allows the use of native vlans. The default native VLAN is VLAN 1, and this can be changed.
B. ISL allows the use of native vlans. The default native VLAN is VLAN 1, and this cannot be changed.
C. 802.1q allows the use of native vlans. The default native VLAN is VLAN 1, and this can be changed.
D. 802.1q allows the use of native vlans. The default native VLAN is VLAN 1, and this cannot be changed.
Answer: C. 802.1q allows native vlans, the default is VLAN 1, and this can be changed with the interface-level command switchport trunk native vlan <x>, where “x” is the desired native vlan.
27. You are running the IEEE 802.1q trunking protocol between two Cisco 2950 switches. One of your switches is receiving frame with no VLAN ID. What action will the switch take with these frames?
A. The frames are corrupt. They will be discarded and an error message sent to the sending switch.
B. These are 802.1q management frames; they will be flooded to other switches on VLAN 0, the Cisco management VLAN for 2950 switches.
C. These frames are destined for the native vlan and will be forwarded accordingly.
D. These frames will be queued while the receiving switch sends a message to the VTP server to see where the frame should be forwarded.
Answer: C. When running 802.1q, the switch will not put a VLAN ID in any frame that is destined for the current native VLAN. A switch receiving frames with no VLAN ID will assume the frames are meant for the native VLAN.
28. What are the three modes a switch running VTP can run in?
29. A VTP client receives an advertisement with a configuration revision number of 56. The client accepts the advertisement. Three minutes later, the client receives a VTP advertisement with a
configuration revision number of 45. What will the client do with this advertisement?
A. Accept it. VTP advertisements with lower numbers are always accepted.
B. Discard it. VTP advertisements with lower numbers are always discarded.
C. Send the advertisement back to the server.
D. Accept it, but send a VTP Query message to the server.
E. Discard it, but send a VTP Query message back to the server.
Answer: B. A VTP client will only accept a VTP advertisement if the revision number is higher than the revision number of the last VTP advertisement it accepted. The revision numbers are incremented by the VTP server anytime VLAN configuration information is sent.
30. You need to add three VLANs to your network. You have two VTP Servers and ten VTP Clients, all in the same domain. What is the
absolute minimum number of devices you need to manually add these new VLANs to?
A. One – one VTP server.
B. Two – both VTP servers.
C. Two – one VTP server and one VTP client.
D. Three – both VTP servers and one VTP client.
Answer: A. Configure the VLANs on one VTP server, and that server will send an advertisement to every VTP device in its domain, including the other VTP server.
31. Which of the following processes reduces broadcast propagation across a trunk?
Answer: D. VTP pruning prevents broadcasts from being send over a trunking line between two switches when the hosts for the broadcast’s destination VLAN all reside on the sending switch. If the remote
switch has no hosts needing the broadcast, there is no reason to send the broadcast over the link.
32. You have just put a brand-new Cisco 2950 switch on your network. You run show vtp status to check the default settings.
Which of the following is true? (Choose two.) A. VTP Pruning is enabled.
B. The VTP password is “CISCO”.
C. The switch is a VTP Server.
D. The switch is a VTP Client.
E. The VTP domain name is “NULL”.
F. The VTP domain name is “VTP1”.
G. The VTP domain name does not appear.
Answer: C, E. The switch will be set to VTP Server mode, the
default. The VTP domain name will be NULL. By default, VTP pruning is disabled, and VTP passwords will not be set.
33. Your network consists of three VTP servers, ten VTP clients, and one switch running in VTP transparent mode. You wish to add a VLAN that will be seen by all the VTP clients. Which of the following best describes where you can add this VLAN and achieve the desired result?
A. A VTP Server only.
B. A VTP Server or a VTP client.
C. The switch running in VTP Transparent mode.
D. You can add a VLAN to any of these clients.
Answer: A. You cannot add a VLAN to a VTP client. You can add a VLAN to a switch running transparent mode, but the VLAN would not be advertised to the other switches. Changes made to a switch in VTP Transparent mode affect only that particular switch.
34. You add a VLAN to a VTP server in VLAN Database mode. After adding the VLAN and using Ctrl-Z to save your change, you run show vlan brief to make sure the VLAN was added. You do not see the VLAN. What is the issue?
A. To exit VLAN Database mode and save changes, you need to use CTRL-H.
B. To exit VLAN Database mode and save changes, you need to type “exit”.
C. To exit VLAN Database mode and save changes, you need to type “reset”.
D. To exit VLAN Database mode and save changes, you need to type “VTP leave”.
Answer: B. VLAN Database mode is different from other modes in that you must type “apply” or “exit” when leaving the mode in order for your changes to be saved. Entering “apply” will save the changes and bump the configuration revision number by 1 and will leave you in VLAN Database mode. “Exit” will do the same and exit VLAN Database mode. Leaving this mode with CTRL-Z will not save changes.
35. You wish to enable trunking between two Cisco 2950 switches.
The switches are physically connected via port fast0/7 on both
switches. On one switch, the port is in dynamic desirable mode; the other side is in trunking mode. What is the result?
A. Because of the mismatched mode types, trunking cannot occur.
B. On Cisco 2950 switches, only ports fast0/1 through fast0/6 can trunk.
C. Trunking will occur.
D. Trunking will occur, but errors will occur when transmitting frames over the native vlan.
Answer: C. If one port is in trunk mode, and the other is in dynamic desirable, trunking will occur. There is no limitation on a Cisco 2950 switch as to which FastEthernet ports can trunk.