Cisco CCNA mock exam questions sample test – Question 8

Which of the following accurately describes the purpose of a trunk?

A. A trunk is used to carry traffic for a single VLAN and is typically used between switches.
B. A trunk is used to carry traffic for a single VLAN and is typically used between a switch and an end-user device.
C. A trunk is used to carry multiple VLANs and is typically used between switches.
D. A trunk is used to carry multiple VLANs and is typically used between a switch and a server.

Correct Answer: C

Explanation:
Trunk links are used between switches to allow communications between hosts that are in the same VLAN, but connected to different switches. Trunk links do not allow hosts in different VLANs to communicate, unless there is an additional trunk link connecting to a Layer 3 device, such as a router or a multilayer switch. Trunk links do allow a host in VLAN 10 on SwitchA to communicate with a host in VLAN 10 on SwitchB. Similarly, a host in VLAN 20 on SwitchA could also communicate with a host in VLAN 20 on SwitchB. A trunk link supports all VLANs by default, and frames that are not traveling on the native VLAN are “tagged” with the VLAN ID of the originating port before being sent over the trunk. The receiving switch reads the VLAN ID and forwards the frame to the appropriate host in the same VLAN.

The other options are incorrect because trunk links do not carry data for a single VLAN, nor are trunks used between switches and hosts (such as workstations and servers).
When a trunk link is extended to a router for the purpose of enabling routing between VLANs, the physical connection that the link connects to is usually subdivided logically into subinterfaces. Then each subinterface is given an IP address from the same subnet as the computers that reside on that VLAN. Finally, each computer in the VLAN will use the corresponding IP address on the matching subinterface of the router as its default gateway. In the example below, the switch has five VLANs created and some hosts connected to it.
If hosts from different VLANs need to communicate, the link between the router and the switch must be a trunk link.

ccna quesion 8

Furthermore, the physical link on the router must be subdivided into subinterfaces and addressed according to the legend shown for each subinterface in the diagram. For example,
the configuration for VLAN 10 shown in the diagram would be as follows:

Router(config)# interface f0/0.10
Router(config-if)#encapsulation dot1q 10
Router(config-if)#ip address 192.168.10.254 255.255.255.0

Finally, each computer in VLAN 10 should have its default gateway set to 192.168.10.254.

Objective:
LAN Switching Fundamentals

Sub-Objective:
Describe and verify switching concepts