Virtual LANs1. In a LAN, which of the following terms best equates to the term VLAN?

b. Broadcast domain

2. Imagine a switch with three configured VLANs. How many IP subnets are required,assuming that all hosts in all VLANs want to use TCP/IP?

d. 3 While a subnet and a VLAN are not equivalent concepts, the devices in one VLANare typically in the same subnet, and vice versa.

3. Which of the following fully encapsulates the original Ethernet frame in a trunkingheader rather than inserting another header inside the original Ethernet header?

b. ISL

4. Which of the following adds the trunking header for all VLANs except one?

c. 802.1Q

5. Which of the following VTP modes allow VLANs to be configured on a switch?

b. Serverc. Transparent

6. Imagine that you are told that switch 1 is configured with the auto parameter fortrunking on its Fa0/5 interface, which is connected to switch 2. You have to configureswitch 2. Which of the following settings for trunking could allow trunking to work?

a. Trunking turned onc. DesirableThe auto setting means that the switch can negotiate trunking, but it can onlyrespond to negotiation messages, and it cannot initiate the negotiation process. So, theother switch must be configured to trunk or to initiate the negotiation process (basedon being configured with the dynamic desirable option.)

7. A switch has just arrived from Cisco. The switch has never been configured with anyVLANs, VTP configuration, or any other configuration. An engineer gets intoconfiguration mode and issues the vlan 22 command, followed by the name Hannahs-VLAN command. Which of the following are true?

a. VLAN 22 is listed in the output of the show vlan brief command.The default VTP setting of VTP server mode means that the switch can configureVLANs, so the VLAN is configured. However, being in server mode, the configurationcommands only show up in the show vlan brief command output, and are not listed aspart of the running-config file.

8. Which of the following commands list the operational state of interface Gigabit 0/1 inregard to VLAN trunking?

b. show interfaces gi0/1 switchportc. show interfaces gi0/1 trunk

9. An engineer has just installed four new 2960 switches and connected the switches toeach other using crossover cables. All the interfaces are in an “up and up” state. Theengineer configures each switch with the VTP domain name Fred and leaves all fourswitches in VTP server mode. The engineer adds VLAN 33 at 9:00 a.m., and thenwithin 30 seconds, issues a show vlan brief command on the other three switches, butdoes not find VLAN 33 on the other three switches. Which answer gives the most likelyreason for the problem in this case?

c. None of the links between the switches trunk because of the default 2960 trunking administrative mode of auto

VTP does not require a password, although if a password is used, the password mustmatch. VTP sends VTP updates immediately after a VLAN database change. However,VTP only sends VTP messages over trunks, and 2960s default to using a trunkingadministrative mode of auto, which does not initiate the trunking negotiation process.So, none of the switches automatically form a trunk, and no VTP messages are sent.

10. Switches SW1 and SW2 connect through an operational trunk. The engineer wants touse VTP to communicate VLAN configuration changes. The engineer configures a newVLAN on SW1, VLAN 44, but SW2 does not

c. VTP pruning enabled and disabled, respectivelyd. VTP modes of server and client, respectively

learn about the new VLAN. Which ofthe following configuration settings on SW1 and SW2 would not be a potential rootcause why SW2 does not learn about VLAN 44?

The domain name and password must be equal, and the switches must connect using a trunk before VTP will work. It is normal to have some switches as servers and some as clients. A mismatched pruning configuration setting does not prevent the synchronization of VLAN databases.

Key Topics■ To create more flexible designs that group users by department, or by groups that worktogether, instead of by physical location■ To segment devices into smaller LANs (broadcast domains) to reduce overhead causedto each host in the VLAN■ To reduce the workload for the Spanning Tree Protocol (STP) by limiting a VLAN toa single access switch■ To enforce better security by keeping hosts that work with sensitive data on a separateVLAN■ To separate traffic sent by an IP phone from traffic sent by PCs connected to the phones

The use of trunking allows switches to pass frames from multiple VLANs over a singlephysical connection. For example, Figure 1-2 shows switch 1 receiving a broadcast frameon interface Fa0/1 at Step 1. To flood the frame, switch 1 needs to forward the broadcastframe to switch 2. However, switch 1 needs to let switch 2 know that the frame is part ofVLAN 1. So, as shown at Step 2, before sending the frame, switch 1 adds a VLAN headerto the original Ethernet frame, with the VLAN header listing a VLAN ID of 1 in this case.When switch 2 receives the frame, it sees that the frame was from a device in VLAN 1, soswitch 2 knows that it should only forward the broadcast out its own interfaces in VLAN 1.Switch 2 removes the VLAN header, forwarding the original frame out its interfaces inVLAN 1 (Step 3).

Command Reference to Check Your Memory

Spanning Tree Protocol