Virtual Lans MCQs with Explanations

Switches do not propagate VLAN information by default; you must configure the VTP domain. VLAN Trunk Protocol (VTP) is used to propagate VLAN information across a trunked link.

Virtual Trunk Protocol (VTP) is used to pass a VLAN database to any or all switches in the switched network. The three VTP modes are server, client, and transparent.

All Cisco switches are VTP servers by default. No other VTP information is configured on a Cisco switch by default. You must set the VTP domain name on all switches to be the same domain name or they will not share the VTP database.

To set a switch port to trunk mode, which allows all VLAN information to pass down the link, use the switchport mode trunk command.

To configure a switch port to use the IEEE standard method of inserting VLAN membership information into Ethernet frames, you would use the dot1q encapsulation method. This method inserts VLAN tags into Ethernet frames according to the IEEE 802.1Q standard, allowing for the transmission of VLAN information across the network. Options A, B, and D are incorrect because: Option A: switchport trunk encapsulation isl configures the switch port to use the Inter-Switch Link (ISL) encapsulation method, which is a Cisco proprietary protocol and not part of the IEEE standard. Option B: switchport trunk encapsulation ietf is not a valid command. There is no encapsulation method called "ietf" for trunk ports in Cisco switches. Option D: switchport trunk encapsulation isl is a command used at the interface configuration level ( Switch(config-if)# ), but it specifies the ISL encapsulation method, which, as mentioned earlier, is not part of the IEEE standard. Therefore, the correct command to configure a switch port to use the IEEE standard method of inserting VLAN membership information into Ethernet frames is Option C: Switch(config)# switchport trunk encapsulation dot1q .

By default, all VLANs are allowed on the trunk link and you must remove by hand each VLAN that you don't want traversing the trunked link.

The valid modes of a VLAN trunk on a switch are dynamic auto, dynamic desirable, trunk (on), and nonegotiate.

You must have the same VTP domain name on all switches in order to share VLAN information between the switches. At least one of the switches must be a VTP server; the other switches should be set to VTP client.

By creating and implementing VLANs in your switched network, you can break up broadcast domains at layer 2. For hosts on different VLANs to communicate, you must have a router or layer 3 switch.

Virtual LANs break up broadcast domains in layer 2 switched internetworks.

ISL is a Cisco-proprietary frame-tagging method. IEEE 802.1Q is the nonproprietary version of frame tagging.

Although you can use either 100Mbps or 1Gbps Ethernet, the 100Mbps is necessary at a minimum and is the best answer to this question. You need to trunk the link from the switch to the router to make this connection work with inter-VLAN communication.

VLANs break up broadcast domains in a switched layer 2 network, which means smaller broadcast domains. They allow configuration by logical function instead of physical location and can create some security if configured correctly.

Cisco has a proprietary trunking protocol called ISL. The IEEE version is 802.1Q.

Only in server mode can you change VTP information on a switch.

This question is a little vague, but the best answer is that the VLAN membership for the port is not configured.

802.1Q was created to allow trunked links between disparate switches.